Want to increase gas mileage cost effectively?
- coast down hills that allow you to maintain your speed
- keep the car a couple hundred RPM above idle in your top gear at cruise (slower than usual highway speeds... probably 45-55 mph range)
- accelerate moderately (you don't want to linger in early gears longer than you have to, but you also don't want to add so much load that the computer significantly richens the AF ratio)
- Don't run the A/C (use the vent from outside instead) - keep windows rolled up
- choose the right tires when you buy them (cheap and hard - soft tires wear faster and have more rolling resistance)
- ensure proper tire pressures (generally 30-35 psi)
- ensure proper functioning of EGR system
- Leaning tune at cruise (if you have the ability to tune already)
effective measures that are not cost efficient
- overinflation of tires (excessive wear in the center of the tires)
(I didn't say overinflation, I said maximum inflation)
- buying a tuner or paying for a tune (a 5% increase in fuel mileage for a $400-$500 tune will take a long time to pay for itself - you're better off investing the money and getting an investment return on it instead)
(It's cost effective if you want to be able to change from a performance mode to a mileage mode without turning your car into a full-time mommy-mobile. It also lets you run lower-octane fuel which in my area is worth about 40 cents per gallon. 1000 gallons and you have paid for it.)
- buying lower gears or a lower O/D such as a .5:1 5th or 6th gear in a car that doesn't already have it (same reasoning as above, unless you can install your own rear gear, in which case you can probably get that done for as little as $100)
- Increasing compression in your motor (increases mileage and should be considered if you're building the engine anyway, but this may also cause you to run higher octane fuel)
- Cams with no overlap and higher dynamic compression ratios: initial cost doesn't make up for the difference in gas mileage over the stock cam, which is already low overlap to begin with
(If you are building a performance engine that breathes better, it's definitely more efficient to start with. In my case, I actually lowered the compression because of the blower. Nobody wants a pansy Mustang 100% of the time)
Ineffective techniques
- tornado
- electrolysis (hydrogen bull****) - takes more power and fuel to create the electricity to split water into hydrogen than you get back out of the hydrogen you just created. Real scientists have been trying to figure out how to split water and then use it for nuclear fusion to create an energy source for decades to no avail (cold fusion). Why would you believe that the internet scammer that promises 80mpg has really figured this out?
- turbocharging: turboing a given motor will not make that motor more fuel efficient. The only reason factories add turbos is so they can run similar power with smaller motors that are more efficient to begin with.
I don't know:
- freer flowing air filters like the K&N: It's not that I don't know if they can increase mileage... That's certainly possible. The question is whether the tune in your car will really allow them too. They will increase volumetric efficiency which will increase power and can increase fuel mileage. Speed density cars will lean out slightly and as a result should increase slightly in mileage. MAF cars should compensate for the extra air and may add more fuel. The result is that you back off of the throttle to sustain cruising speed. I think this will result in an increase in fuel mileage, and they certainly advertise one. I would like to actually test the theory myself, though. (I have tested in on several vehicles over the last 20 years and it has made differences of 1-2 miles per gallon to 3-4 when combined with synthetics, even more with retuning at the cost of power)
- running thinner oil - should increase mileage by increasing mechanical efficiency, but may not protect the motor as well as the thicker stuff, which means what you gain in mileage you pay for in a premature rebuild down the line.... I dunno
- synthetic oil - between increased protection and fuel efficiency there are some definite advantages... price is a definite disadvantage.... over the long run it's hard to say whether sythetic is more cost effective than running premium regular oil (it's more cost effective when combined with 10,000 plus mileage changes and reduced wear on the engine. Put it in the tranny and it's even better. One car, 1987 Mercury Cougar with a 6-cylinder engine, when combined with everything else, went from 24mpg on the freeway to over 32 average. City driving went to about 21-22.
This isn't all inclusive... Just some observations of a guy that's thought through these things before.
Thoughts on my list?
