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improving vehicle mileage

Peter DeJay


Joined: Aug 10, 2011
Posts: 104
Location: Southern Oregon
Great thread! Loved the "mad Max" vehicle mods on the truck Bakari! I had an 83 ford diesel, those are powerful engines! Currently I have a 93 dodge diesel truck that I plan on having for a long time so I'm interested in modding it for longevity as well as max efficiency. One such mod that popped in my head and that I think pertains to Tel's question about engine wear is a dry sump oil resevoir. Its multiple pumps allow precise oil delivery without the crankshaft having to slog through too much oil, robbing HP. Like a turbo, the only reason to not have one is the financial aspect. In my mind that's the only downside I see to frequent starting and stopping of the engine, is that first few second of start up when there is not adequate oil where it's needed.

Another point regarding larger diesel engines especially, is i do believe its important to allow a few minutes of warm up to ensure proper lube, and another thing to keep in mind is allowing a few minutes of no load cool down at the end of the day. Duration depends on weather and how hard it was used, but this allows the oil to cool down the engine evenly so you don't get different areas of the engine block cooling down faster then others and possibly cracking. This would work out perfectly if you are running on SVO as you could use the time to switch tanks to prepare for tomorrows start up.

I've wanted to do an electric fan conversion for awhile, that seems like another simple mod that would bring noticeable improvements. I will definitely look into a manual steering conversion, but I'm not sure if i'll be able to ditch the alternator, but kudos for making it work for you Bakari!
tel jetson
steward

Joined: May 17, 2007
Posts: 3098
Location: woodland, washington
    
  53
Peter DeJay wrote: Another point regarding larger diesel engines especially, is i do believe its important to allow a few minutes of warm up to ensure proper lube, and another thing to keep in mind is allowing a few minutes of no load cool down at the end of the day. Duration depends on weather and how hard it was used, but this allows the oil to cool down the engine evenly so you don't get different areas of the engine block cooling down faster then others and possibly cracking. This would work out perfectly if you are running on SVO as you could use the time to switch tanks to prepare for tomorrows start up.


personally, I think I'm better off plugging in a block or coolant heater a couple hours before starting than I am letting it idle to warm up. adding a pre-oiler pump would improve things dramatically in that regard, too. the same pump could be set up to continue pumping oil for a few minutes when the motor is shut off. in many of these diesel engines, engine oil is doing almost as much cooling as the coolant is, so pumping the oil at shutdown can do a very good job of cooling things down. this would be even more important if there's a turbocharger involved, because those bearings are entirely oil cooled and will burn up quickly if the motor is shut down hot.

one thing I'm definitely doing is adding a larger oil filter at the next oil change. Bakari and I have motors that will accept the filter spec'ed for the mid-90s 7.3-liter Powerstroke diesels. the filter is larger, so there's more actual filter element to better clean the oil and it adds an extra quart of capacity to the oil system. that extra capacity shouldn't really slow the engine warming up, but it will slow how fast the oil gets really hot, which can only be good. the one disadvantage is that our oil filters are on the bottom of the motor, and the bigger filter will stick down a couple of inches lower, so it's a bit more vulnerable.


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Bakari Kafele


Joined: Mar 17, 2012
Posts: 14
tel jetson wrote:
Peter DeJay wrote:Bakari and I have motors that will accept the filter spec'ed for the mid-90s 7.3-liter Powerstroke diesels. the filter is larger, so there's more actual filter element to better clean the oil and it adds an extra quart of capacity to the oil system.


I wasn't aware of that! I'll be doing the same now on my next change
John Polk
steward

Joined: Feb 20, 2011
Posts: 6593
Location: Moving to: NE Washington USDA zone 5 Western steppes to the Rockies
    
135
If there is space inside the filter housing, you might consider sticking a small magnet (or 2) in there to pick up any metal shavings/dust that naturally occurs as the oil passes through the engine.

tel jetson
steward

Joined: May 17, 2007
Posts: 3098
Location: woodland, washington
    
  53
John Polk wrote:If there is space inside the filter housing, you might consider sticking a small magnet (or 2) in there to pick up any metal shavings/dust that naturally occurs as the oil passes through the engine.


I've seen magnets sold that wrap around the screw-on filter. I like the idea. I'll probably do it.



something else I should mention regarding turbochargers: if you've got a turbo, don't do pulse and glide with the ignition off. unless there's an auxiliary oil pump to keep cooling the turbocharger, the bearings would be cooked in very short order and dreams of increasing fuel economy will be forgotten in favor of more pressing issues.
Andrew Parker


Joined: Feb 13, 2012
Posts: 350
Location: Salt Lake Valley, Utah, hardiness zone 6b/7a
    
    4
How much fuel do you save turning off a diesel, rather than idling it without a load? I remember someone once telling me that idling a big semi tractor overnight to keep the heater or air conditioner going took maybe a quart of fuel.
Bakari Kafele


Joined: Mar 17, 2012
Posts: 14
Andrew Parker wrote:How much fuel do you save turning off a diesel, rather than idling it without a load? I remember someone once telling me that idling a big semi tractor overnight to keep the heater or air conditioner going took maybe a quart of fuel.


Most sources I've found say that a big semi tractor uses a gallon of fuel per hour to idle.
It is illegal in almost 1/4 of US states for them to do that anymore, because it is so insanely wasteful and polluting.

It is not as bad with a smaller engine, and I don't know the exact numbers, but there is really no circumstance where it ever makes sense to idle for more than a minute (including for "warm up" - modern engines do not need to warm up at all)

For more: http://www.transportation.anl.gov/pdfs/TA/374.pdf
and: http://www.transportation.anl.gov/pdfs/EE/642.PDF
Bakari Kafele


Joined: Mar 17, 2012
Posts: 14
tel jetson wrote:
I've seen magnets sold that wrap around the screw-on filter. I like the idea. I'll probably do it.



something else I should mention regarding turbochargers: if you've got a turbo, don't do pulse and glide with the ignition off. unless there's an auxiliary oil pump to keep cooling the turbocharger, the bearings would be cooked in very short order and dreams of increasing fuel economy will be forgotten in favor of more pressing issues.


I just stick a magnet directly to the metal body of the filter itself. Same effect, no money spent on a rubber ring to hold the magnet.

If you have an automatic you shouldn't coast engine off either.

And if you have power steering, you should be aware that the steering feel will change with the engine off.

The good news is that coasting with the engine on (at idle) still saves fuel compared to holding down the gas at all times, as their is no load and RPMs drop to the minimum.
tel jetson
steward

Joined: May 17, 2007
Posts: 3098
Location: woodland, washington
    
  53
Andrew Parker wrote:How much fuel do you save turning off a diesel, rather than idling it without a load? I remember someone once telling me that idling a big semi tractor overnight to keep the heater or air conditioner going took maybe a quart of fuel.


a lot of bigger vehicles have a diesel-fueled coolant heater. burns diesel efficiently in a little contraption about the size of a lunch box and pumps coolant through it. keeps the motor and cabin warm. can also be used to heat up a diesel motor or cabin before it's started. uses magnitudes less fuel than running the motor. initial cost can be over $1000, but on a big motor, it doesn't take long to make that up in reduced fuel costs.
tel jetson
steward

Joined: May 17, 2007
Posts: 3098
Location: woodland, washington
    
  53
Bakari,
how difficult was the steering conversion? I'm suffering the usual Ford power steering obnoxiousness, and manual steering would suit me just fine. I just don't really know what's involved in installing a manual gear.
Bakari Kafele


Joined: Mar 17, 2012
Posts: 14
tel jetson wrote:Bakari,
how difficult was the steering conversion? I'm suffering the usual Ford power steering obnoxiousness, and manual steering would suit me just fine. I just don't really know what's involved in installing a manual gear.


It all depends on your car.

I can speak for an older large truck, and a modern compact Toyota.
I suspect that many (maybe most) vehicles will be similar to one, the other, or some combination thereof, but I am not a mechanic or an expert on the topic.
In either case I definitely recommending buying or borrowing the Chilton and/or Haynes manual for your specific car (will easily pay for itself it not-going-to-the-mechanic over the years)

I'll start with the modern one, because it was simpler

2006 Toyota Matrix:
Most modern cars don't come with manual steering as an option. In other words, power steering comes standard on even the base model.
(This is the stupidist and most wasteful thing that is nearly universal that I can think of, but I'm going to try not to rant to the converted)
This means it may be difficult to find a manual steering gear, and it may be impossible.
(A steering gear meant to be manual has a lower gear ratio, so you turn the wheel further to make the drive wheels move a given amount. Since with power steering the engine does all the work for you, the manufactures make smaller steering wheels which don't have to turn as far to turn the drive wheels)

On the plus side, compact to mid-size cars are really pretty easy to steer even when using an unpowered power steering gear. The only time you will really notice it is when parallel parking, just like with a dedicated manual. I can't speak for how easy or hard it may be to steer a full-size car or SUV with an unpowered power steering gear.

The fact that a manual gear compatible with a modern car may be difficult or impossible to find is actually what makes the process easier.

Step 1: Find the power steering pump. Easiest way is to start from the point you fill the fluid, and trace the lines.
Step 2: Disconnect all the lines going to and from it. Fluid will drain out. Be prepared to catch the fluid in a container for proper disposal (mechanics, autoparts stores, and recycling centers will accept automotive fluids for free)
Step 3: Trace the lines that come off the pump and go downwards toward the steering axle. Disconnect and drain those, as above.
Step 4: Once (almost) all the fluid is drained, reconnect the lines so that dirt doesn't get in there. You won't get 100% of the fluid out, which is a good thing because it lubricates the steering gear. Ideally you should loop the two ports of the steering gear directly to each other.
Step 5: Find a belt diagram for your engine. If you can't find one, draw your own. Make note of which pulley runs what (esp the power steering pump) as well as which direction they go. That last part is important!
Step 6: Figure out how a belt could hypothetically run across the pulleys while skipping the power steering pump, and nothing else (except any idler pulleys, if that works out better). If it has individual V-belts, this is pretty easy. If it uses a serpentine belt, this can be tricky, depending on the layout of the particular engine. You may have to skip the tensioner (I did). Trace out a path that will make everything turn the correct direction while skipping the PS pump. Measure the distance around the pulleys in the new set-up you just traced - use a or belt or any other long flat flexible thing and actually wrap it around. This measurement needs to be accurate. Measure in millimeters, to the millimeter.
Step 7: Go to the local autoparts place, and give them that measurement, along with the number of ribs on the original belt. (If the PS pump had its own separate V-belt, you can skip this step)
Step 8: Somehow get the new belt in place. This was neither easy nor fun. And I had to go back to exchange the belt twice because it wasn't the exact right size. But it did work out eventually.
Step 9: Enjoy your gas savings and (extremely minor) arm work-out

Seems like a lot when I write it out, but it was all a few hours (annoying and moderately stressful) work
In fact, my girlfriend (its her car) - whose previous auto machine experience was one oil change and one flat tire change - did the first 4 steps on her own (I was out of state, and coached her by phone)
Without the fluid to resist movement, it is much easier to turn the steering wheel than the impression you get by trying to steer with the engine off.


1983 Ford truck:
Steps 1-3 are the same.
Step 4: Remove the power steering pump, and all of the lines attached to it
Step 5: Disconnect the recirculating ball steering gear from the steering axle
Step 6: Disconnect the steering gear from the steering column - some older vehicles this may be one piece, in which case you have to remove the steering wheel - you can borrow a special puller for free at most autoparts stores
Step 7: Remove the entire steering gear. Its heavier than it looks.
Step 8: Attach the manual gear exactly where the power gear just was. I found mine at an auto wreckers. Depending on the car, and how common manual steering was as an option, you might find one at a U-Pull-It kind of place, or on ebay, or whatever. You can find them in decent shape, since others pull them out fully functional in order to "upgrade". Lazy pathetic Americans...
Step 9: Reattach steering column, steering wheel if applicable
Step 10: The belt issue should be much easier if its a vehicle that came with manual as an option all along. V-belt, you are done. Serpentine belt, just tell the person at the parts store your model of car and that it has manual steering, and the computer should spit out the right size belt, so you don't have to do any measuring or diagram drawing.
Step 11: enjoy your gas savings and (even more minor) arm work out!

The longest part of the process was finding a manual steering gear.
Having had 4 vehicles with manual steering (including my current F-250 and a 15ft camper van) and 2 with, I would never not do this to any I ever owned.
tel jetson
steward

Joined: May 17, 2007
Posts: 3098
Location: woodland, washington
    
  53
that sounds reasonable. mine is an '86 F-250. so it sounds like I just have to find the steering gear to swap out. I can probably handle that and pulling the existing power steering equipment.
Marcos Buenijo
pollinator

Joined: Dec 18, 2011
Posts: 583
Location: Southwest U.S.
    
  12
paul wheaton wrote:Next, I'm kinda curious: would it not be possible to have a MUCH smaller engine and get far superior mileage? Granted, there would be less acceleration power, but this guy is already doing lots of stuff to go easy on acceleration.


Yes, that is true. Don't listen to anyone who argues otherwise. The efficiency of gasoline and Diesel engines vary a lot over their power range (especially gasoline engines). Most of this loss is due to friction. The engine works most efficiently when the average cylinder pressure is at a maximum. With gasoline engines this means a fully opened air throttle valve because gasoline engines always operate at a constant air/fuel ratio. This condition rarely occurs in an automobile engine because the car engine has to be large enough to provide the acceleration and hill climbing capabilities (i.e. the torque) necessary for adequate performance. So most of the time the air is throttled down to lower the average cylinder pressure (and engine torque) to maintain cruising speeds. Well, the friction of an engine is very nearly directly proportional to its speed. So, an engine that is 25% efficient at a given speed with the throttle fully open still sees the same friction when the engine is operating at a fraction of the power that the engine is capable of at the same engine speed. An engine uses about 20% of its power just to overcome friction. Well, this means throttling down the engine to 1/2 the power it's capable of at a given speed has gone from 80 units of useful work plus 20 units of friction down to 40 units of useful work plus 20 units of friction. Do the math. The efficiency drops. It only gets worse the more throttling you do. There are other factors to consider, but this dynamic explains a lot. The gains in mileage from using a smaller engine would be particularly apparent during city driving where the engine is throttled down a great deal. The best mileage would likely be had from a series hybrid configuration that uses a very small highly turbocharged Diesel engine that also incorporated engine shutdown at low speeds and regenerative braking. But I wonder how much it would cost? Could just go with a Diesel, but how much will it cost (especially after all the emissions controls equipment are installed per EPA and other regulations)?

There's all kinds of ways to improve efficiency. However, most of them are expensive and not likely to prove economical in practice unless someone drives a great deal. If someone doesn't drive too much (or too little), then the idea I personally like is to dual fuel a vehicle with a small wood gasifier. Yeah, I know it's not practical for most people. However, a small gasifier just large enough to maintain low cruising speeds would be remarkably compact, yet it would reduce fuel consumption by 80% or more. Plus, you have a small gasifier available for all kinds of interesting applications. Check out Vulcan Gasifiers to see an example of a compact gasifier that might be suitable for this purpose. It's based on the Imbert design that was originally developed for vehicle applications. NOTE: Converting a Diesel engine to dual-fuel with wood gas would be a lot simpler, but either one can and has been done. Check out Wayne Keith's site at www.driveonwood.com.
Bakari Kafele


Joined: Mar 17, 2012
Posts: 14
Marcos Buenijo wrote:
paul wheaton wrote:Next, I'm kinda curious: would it not be possible to have a MUCH smaller engine and get far superior mileage? Granted, there would be less acceleration power, but this guy is already doing lots of stuff to go easy on acceleration.


Yes, that is true. Don't listen to anyone who argues otherwise.


It is true for most modern cars sold in America. It is not true in my truck. My truck is 5500lbs empty, and up to 10,000lbs full, but has less than 170 horsepower peak. Its not quite as slow in acceleration as a fully loaded semi-truck, but, unlike newer cars and trucks, it is not overpowered either. Today the average car - not truck, not sportscar - has 225HP. For trucks its somewhere around 350HP. This is one of the largest reasons why US mpg standards are so ridiculously terrible compared to the rest of the world. Modern cars are not built for "adequate" performance. They are all built to be high performance racing machines - even the station wagons, minivans and compact commute cars. And we can't blame the auto manufactures alone; they build more of whatever consumers buy. They stopped producing the 3 cylinder, 50mpg Geo Metro and the 2 seater original Honda Insight because they weren't selling.

You have the right idea in your calculations, but an engine that is 25% efficient isn't just losing 25% of its energy to internal forces, it is losing 75%. The efficiency % is the amount of power actually produced from the fuel, not the amount of loss. So its actually much worse than your example implies.
You are correct that having a hybrid engine helps mainly because it allows you to have a smaller engine and use it at higher load. This is also the reason that the pulse and glide driving technique works (despite the fact that it taks more energy to accelerate than it does to stay at a constant speed). Pulse and Glide driving allows you the advantage of minimizing engine on time (allowing you to save that 75% of frictional and pumping losses), while running the engine under higher load when it is on - and unlike a hybrid system, it is entirely free (disclaimer - don't try this at home unless you know what you are doing. search ecomodder.com for details)
Marcos Buenijo
pollinator

Joined: Dec 18, 2011
Posts: 583
Location: Southwest U.S.
    
  12
Bakari Kafele wrote:It is true for most modern cars sold in America. It is not true in my truck. My truck is 5500lbs empty, and up to 10,000lbs full, but has less than 170 horsepower peak. Its not quite as slow in acceleration as a fully loaded semi-truck, but, unlike newer cars and trucks, it is not overpowered either. Today the average car - not truck, not sportscar - has 225HP. For trucks its somewhere around 350HP. This is one of the largest reasons why US mpg standards are so ridiculously terrible compared to the rest of the world. Modern cars are not built for "adequate" performance. They are all built to be high performance racing machines - even the station wagons, minivans and compact commute cars. And we can't blame the auto manufactures alone; they build more of whatever consumers buy. They stopped producing the 3 cylinder, 50mpg Geo Metro and the 2 seater original Honda Insight because they weren't selling.

You have the right idea in your calculations, but an engine that is 25% efficient isn't just losing 25% of its energy to internal forces, it is losing 75%. The efficiency % is the amount of power actually produced from the fuel, not the amount of loss. So its actually much worse than your example implies. You are correct that having a hybrid engine helps mainly because it allows you to have a smaller engine and use it at higher load.


The low rated power of your engine illustrates the dynamic I discussed. In other words, your post reinforces my argument. There is no contradiction here. Also, I did write "there are other factors to consider" (these include power transmission losses, vehicle speed, tire friction, aerodynamics, thermal losses from cylinder, piston ring blow by, etc.), and please note that losses are implied in any efficiency calculation (net power out implies the losses, and vice versa). Bottom line, it seems we're saying the same things in different ways. I agree with all your arguments, in particular that people seem to want to have their cake and eat it too. They want powerful cars, super fuel economy, and low sticker price... and beach front property in Arizona!

Seriously, I have no doubt that the fuel economy you get in your truck could be improved with an even smaller engine that is optimally geared (especially a Diesel). However, I DO NOT think it makes sense to do this... I'm merely making the argument to illustrate the physics. What you have in the truck now seems to be the best compromise. Buying the smallest/lowest powered vehicle that does the job gets all the low hanging fruit with respect to net fuel savings, and that's what matters most.
Bakari Kafele


Joined: Mar 17, 2012
Posts: 14
Marcos Buenijo wrote:
The low rated power of your engine illustrates the dynamic I discussed. In other words, your post reinforces my argument.


Oh for sure! I didn't mean to imply I was contradicting you, I totally 100% agree with your first post. My personal example not withstanding (the truck was made in 1983), I actually meant to reinforce what you were saying and then some.

For example, on the efficiency issue: when discussing internal combustion engines, the efficiency reported is generally that of the engine alone. Most gasoline engines are only 25% efficient, meaning they lose 75% of the energy contained in the fuel to heat from the internal friction force of turning the engine itself.
Drive train losses, power accessory loses (alternator, power steering, A/C, etc) are ON TOP of that. Then, rolling resistance and aerodynamic losses are on top of that.
Once you factor in that a car typically weighs 2000lbs or so, and a driver weighs maybe 200lbs - which means most of the energy that finally makes it to moving the vehicle is moving the mass of steel more than the driver - you are left with approximately 1% of the energy in the fuel being used to actually transport the person.
Making it one of the most wasteful ways to get from one place to another that one could imagine.
Dale Look


Joined: Mar 07, 2012
Posts: 27
Here is a hybird that I would like to own.
http://www.oshkoshdefense.com/products/12/hemtt-a3-diesel-electric#overview
Mark Rose


Joined: Jul 19, 2009
Posts: 37
    
    1
Bakari Kafele wrote:
Marcos Buenijo wrote:
paul wheaton wrote:Next, I'm kinda curious: would it not be possible to have a MUCH smaller engine and get far superior mileage? Granted, there would be less acceleration power, but this guy is already doing lots of stuff to go easy on acceleration.


Yes, that is true. Don't listen to anyone who argues otherwise.


It is true for most modern cars sold in America. It is not true in my truck. My truck is 5500lbs empty, and up to 10,000lbs full, but has less than 170 horsepower peak. Its not quite as slow in acceleration as a fully loaded semi-truck, but, unlike newer cars and trucks, it is not overpowered either. Today the average car - not truck, not sportscar - has 225HP. For trucks its somewhere around 350HP. This is one of the largest reasons why US mpg standards are so ridiculously terrible compared to the rest of the world. Modern cars are not built for "adequate" performance. They are all built to be high performance racing machines - even the station wagons, minivans and compact commute cars.


I have a "compact" car, a Chevrolet Optra5, also sold as a Suzuki Reno in the US. It has a 2.0L 120 HP engine. It's adequate. Acceleration is decent over 3000 rpm. I've towed 2000 lbs with 1000 lbs in the car and maintained highway speeds by gearing down and keeping the RPM around 4000. In my next vehicle, I'd probably want more power.

Cars get crappy mileage in general. The Pipistrel Virus SW with the 100 HP Rotax 912 iS engine burns about 5.5L/100 km (43 mpg) -- at 274 km/h (170 mph)! My car tops out at about 170 km/h, and I sure don't get that kind of mileage.
Mike Turner


Joined: Sep 23, 2009
Posts: 154
Location: Upstate SC
    
    1
paul wheaton wrote:So with the aerocivic:

Started off averaging in the mid 40s. So I'm gonna just say 45.

Then, with hypermiling, you got it into the high 50s - so I'm gonna say 58.

And then there are the modifications to the shape. And the modifications to the engine. And at 55, you get better than 100mph.

So I'm gonna guess that before the engine change, you got it up to 94. And after the engine change you got it about 102.

Is that about right?



I just came across this thread. The aerocivic is my car and is a 92 Honda Civic hatchback that I started modifying in 2005 to increase its mileage. In stock configuration it averaged mileage in the high 40's (summer), low 40's (winter), would get 50mpg on a summer highway trip at 55mph and around 40mpg on 70mph trips. By hypermiling it, I was able to get mpg's into the mid to upper 50's and occasionally break 60mpg the summer, but had to keep my speed below 50mph to do it. I finally got tired of the speed restriction for getting good mileage, so I started aeromodding the car to reduce its aerodynamic drag (which is the dominant load on the engine at highway speeds) and by this was able to get the average mileage in the low-mid 70's (summer) and mid-high 60's (winter). The final improvement was installing a Honda lean burn engine in the car when my existing motor wore out and this added 3-4 mpg to the average. In the summer on a flat road I can cruise along at 55mph while getting 100mpg, get mid 70's mpg on 70mph trips, and get low 60's on 80mph trips. I spent about $400 on materials to aeromod the car and have so far saved well over $5000 in gas over what it would have cost me in gas at the car's stock mileage. Fringe benefits of the new aerodynamic shape are that I don't have to clean dead bugs off the front any more, the low curved front end sends collided deer up and over the top of my car with little damage to the front of my car, the rounded aerodynamic shape is a poor reflector of radar, and the interior of the rear boat tail doubled the cargo space behind the back seat. aerocivic.com has more info about the car.
jack vegas


Joined: Mar 09, 2013
Posts: 14
Location: Edge of the World - PNW
    
    1
There are 3 primary ways of improving the MPG of an existing vehicle:
1 - Reduce drag. Streamline body and add belly pan under car to reduce aero drag. Use narrower harder tires to reduce rolling drag. Remove unneeded engine accessories, air conditioning,etc., to reduce engine drag.

2 - Reduce weight. Strip all unnecessary material. Don't drive with a full tank. Maybe replace side and back windows with lighter plastic instead of glass (I think only the windscreen needs to be glass to be legal - not sure though).

3 - Adjust the nut behind the steering wheel. This is what hypermiling is all about. Drive the speed limit or a bit less. No jackrabbit starts or rapid acceleration. Minimize braking. Plan stops and accelerations in advance so throttle can be applied more appropriately. Coast whenever possible. Basically drive like an old person. We drive that way to extend the lives of our cars and ourselves.
 
 
subject: improving vehicle mileage
 
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