I've got gas, and you can too! Getting Better Gas Mileage by a Mechanic

Question: I can’t afford a new car, and the price of gas is killing me. How can I get the most mileage out of the car I already own?

This question was asked of me recently as the price of gasoline is above four dollars and the price of diesel requires you to take a second mortgage out on your home before tanking up. Obviously, everyone doesn’t have the financial means to purchase a new vehicle, even though OPEC seems to think we do. Thus I will list the things you can do and have done to maximize your mpg.

First off, I would like to preface this with a no-nonsense disclaimer. You will not get 50mpg out of a carbureted big block V-8 without spending more on the conversion than you would on fuel anyway. Is it possible? Yes. Is it expensive? Very. Is it so expensive that it is probably out of reach for someone who can’t afford a new car? Yes. So…the following is a list of things you can do to improve your gas mileage without breaking the bank.

Keep your tires fully inflated to the tire sidewall pressure. (where it says XXpsi (cold) Tires that are low on air require more energy to turn because there is more rolling resistance between them and the ground. The more energy your engine has to use, the more fuel it will burn.

Lighten your vehicle. It is easier than you think. Go through your trunk and remove everything that you haven’t used within the last six months except the spare tire and jack. The less weight there is in your vehicle, the less power it takes to move it and the less fuel you will burn. If you have AAA coverage, you can take out the spare and the jack too but make sure to replace them before a long trip.

Use the air conditioning sparingly. The air conditioning system on a vehicle take a lot of energy away from the engine and burns a lot of fuel, so use it sparingly. If you are in city traffic, roll down your window instead. If you are on the highway turn the A/C on for a few minutes and then turn it off. Rolling down your window on late model cars while on the highway actually burns more fuel than running the air conditioning because of wind resistance.

Turn off your car. If you are waiting in a drive-thru or waiting for someone, turn off your car. There is an old saying that starting your car burns more fuel than just leaving it run. This is false. It also doesn’t cause that much more wear and tear on the engine so the greatest benefit is to turn the car off

Ease up on the throttle. Acceleration burns more gas than driving at a constant speed, so avoid fast starts and don't exceed the speed limit on the highway.

Drive conservatively. Leave a bit more distance between you and the person ahead of you in stop and go traffic. That way when the person in front of you stops you can take your foot off of the accelerator and coast for a bit. If you have left enough room then by the time you get to where you would have stopped anyway, the person in front of you has probably already sped up again. This has an added effect that it causes less wear to your braking system and actually helps clear up traffic because the person behind you will see that your brake lights not come on and will maintain a more consistent speed. Plus it is a safer way to drive because it give you more reaction distance should the person in front of you slam on their brakes.

Change your oil and air filter regularly but not your spark plugs. Huh? Don’t change my spark plugs? Your engine oil reduces friction in your engine, less friction means less energy used to keep the engine running so less fuel used. Your air filter, when it is dirty, can cause the engine to run a little rich causing you to lose power and burn more fuel. As for the spark plugs…New spark plugs have less resistance to make a spark than old ones as old ones have built up carbon on them from burnt fuel. That extra resistance causes a hotter spark to overcome the resistance of the carbon deposits on the electrodes, which causes the fuel/air mix to burn hotter and causes the ignition timing to advance very slightly. Which will produce a bit more power and a bit less fuel consumption. So only change your spark plugs if one or more is not working.

Get a tune up. Your local mechanic (or you) can perform a tune up on your car that will make the engine run more efficiently and useless fuel. The typical tune up consists of: New PCV valve, new EGR valve, oil and filter change, re-time the engine and adjust the valves.

Lube your drive train. Your local mechanic (or you) can perform a full drive train lube and service which consists of removing and replacing the differential and transmission oil and lubricating the suspension, driveshaft and steering linkages. This will reduce friction in the drive train, requiring less energy to make things move. It will also cause your bearings, bushings and seals to last longer.

Service your bearings. Your local mechanic can service your axle bearings which will remove a lot of friction from your drive train. It is not uncommon to get 30-70 more miles per tank of fuel with new or serviced bearings. Since this usually requires removing the wheels, hubs, jackshafts and brake assemblies I recommend having a professional mechanic do this service unless you know what you are doing. If your bearings are sealed cartridge bearings, have them replaced. If they are loose “cup and cone” or “cup and race” bearings, have them inspected, cleaned, lubed and re-installed or replaced if necessary. Ensure the mechanic uses a torque wrench to achieve proper bearing pre-load (a lot of them just tighten until the wheel doesn’t turn and then loosen ¼ turn, this is incorrect)


Finally, if you just need to go up to the store on the corner, or run a quick and close errand, consider walking, biking, roller-skating, jogging, walking on your hands, riding a scooter or skateboarding instead of using your car. Even the most efficient hybrid car in the world gets worse fuel mileage than you do.


Grimy Handshakes,
The Motachanic

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