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Discussion Starter #1 (Edited)
Ok, I thought I'd make a huge list of things you can do to improve your gas mileage since everyone is always asking about this. So go ahead and post your suggestions and I'll just keep editing the first post to include them all. Thanks!

External Factors

1. It goes without saying, don't race your car around. Drive conservatively.
2. Keep it under 70mph. (wind resistance + high rpm in cruising are bad)
3. Drive with your windows closed. (wind resistance)
4. Stop using the A/C so much... or at least get it checked to make sure it's still efficient.

Suspension

1. Get an alignment! Anything that prevents your car from rolling straight will rob power and create resistance (from your tires wearing out prematurely).

2. Fix your bushings! This is my own belief and here's why... I had a bunch of crap in my back seat and trunk that was weighing my car down. Now you might think it was just the weight, but I think it's also why my rear tires have worn out prematurely. During this time I also had severely bad gas mileage (25-30 mpg). Somehow, my tires had negative camber with all the weight because all the wear was on the side walls on the outside. I since removed the boxes and crap and magically my gas mileage is improving (without fixing the bushings... yet).

3. Check your tire pressure to make sure it's right.

4. Make sure brakes are in good order and not sticking. This goes for the emergency brake too. Lift your car up and try to spin the wheels. If they have any resistance (they slow down too fast) then something is wrong.

Engine

1. Get a new o2 sensor. If they go bad, you will definitely have bad gas mileage. But if they're giving low voltages because its dirty, your ecu will think you are going lean and will dump more fuel to compensate. Check your muffler tip to see... it will be BLACK, not dark gray.

2. Change your PCV valve.

3. Check and correct your timing at the distributor with a timing light.

4. Get rid of that eBay chip. It's crap... go back to stock or get it professionally tuned.

5. Change/clean your air filter. Get a K&N to replace a stock air filter.

6. If you're turbo, get rid of the FMU and the piggyback. Get a professional tune using Crome/Uberdata/Hondata/Turboedit/Neptune. Or do it yourself with a wideband o2 sensor.

7. A clogged fuel filter will ruin your mileage.

8. Check valve lash when the manual says to.

9. Check/change spark plugs. All you need are NGK copper V-power plugs. Nothing fancy.

10. Don't wait forever to change your oil. Also watch oil level.
 

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Check your tire pressure to make sure it's right.
A clogged fuel filter will ruin your mileage.
Check valve lash when the manual says to.
Spark plugs too.
Don't wait forever to change your oil. Also watch oil level.
Make sure brakes are in good order and not sticking.
 

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Discussion Starter #3
thanks.. added :TU:
 

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Less of a contributor but still relevant... stay with stock size tires, or be conservative in your tire size choice. Larger rims have a higher moment of inertia, aka they have more angular momentum at speed and take more energy to accelerate. Also wide tread widths (common on large rims) add friction.

Get rid of the ricer wing if you got one. Air resistance = bad.
 

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Would an old or fading alternator or fuel pump adversely affect milage? I get crap milage (27/33 w/ a Y8 swap) and my fuel pump is struggling and I suspect my alternator is about to go.
 

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Lower you car, reduces wind resistance

If you do not have a/c, put a block-off plate where the condencer would be (only if it will not block air flow to the radiator) I increased my fuel economy by 3-4 mpg w/ this one.

Reduce the weight of your car.

Run higher air presure in your tiers, I run 40psi, reduces roling resistance.

Keep your car clean & waxed, reducess wind resistance.
 

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my name says Guest, but Im really a MEMBER
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I'm all about gas mileage. From my experience:

ease into the throttle, mashing the throttle kills gas mileage.
don't brake on turns :) use the momentum.
Don't race to stop at a red light
Coast
I tend to get better gas mileage if I keep 1/4 to 1/2 tank in all the time.
60 on the freeway unless your in a hurry. personally I go 65 max.
Def. as extensive of a tune-up as possible.
Doesn't an exhaust and little timing help????
get into 5th gear ASAP.
 

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i heard tornado's are pretty good too.
 

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V-TEC said:
run premium gas. its more pure and in turn will raise gas milage and prolong the life of your engine.
I don't think that's correct, i'm pretty sure you're supposed to run the gas that's right for your car. If you're not tuned for that type of gas, or if your compression ratio doesn't call for it, then you will recieve no benefit from running a different octane of gas.
 

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samuraiz said:
I don't think that's correct, i'm pretty sure you're supposed to run the gas that's right for your car. If you're not tuned for that type of gas, or if your compression ratio doesn't call for it, then you will recieve no benefit from running a different octane of gas.
You'r correct. The only benifit of higher octain the the resistance to detonation due to compretion
 

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i heard running cheap gas leaves deposits in your engine and cause trouble down the line, the premium stuff is supposed to keep things clean. I used to own an MX3 that i put premium in, once i tried to go back to cheap gas, the car literally shut off on me a few days later when i pulled out of a parking space.
 

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V-TEC said:
run premium gas. its more pure and in turn will raise gas mileage and prolong the life of your engine.
Even the 9.6:1 compression ratio of a y8 isn't enough to properly burn premium. I tried it. Even advancing dizzy timing as far as it would go-- 16 degrees-- it didn't get hot enough. I had carbon up the WAZOO and killed my new plugs in a month. To boot, my mileage went DOWN by about 3mpg or so on extended trips. I could only get ~31 or so, and that was ~60mph.

It took a few weeks driving afterwards on regular fuel at stock timing before the pinging from the carbon hotspots finally went away. Eventually my mileage went back to where it was supposed to be.

This issue has been killed time and time again. Search and see, regular fuel is the stuff unless you build the motor to where you absolutely can't run it.
 

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just a useful tid bit of information about the wind resistance: There is double the wind resistance driving at 70 mph compared to that of 55 mph. Alls it takes is 15 mph to double the resistance, so dont drive like a bat out of hell.
 

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Although running the tire pressures too high will cause uneven tire wear, and poorer ride quality, the higher the air pressure, the better the mpg. As long as you do not exceed the max psi. For extra long trips I usually put an extra 5 psi in... This reduces the amount of energy wasted in causing the tire to flex.

Although driving slower and smoother does increase your mileage, I haven't found a major highway where the prevailing speed of traffic is much slower than 80mph... Driving at 55mph in this instance is dangerous so I wouldn't recommend it unless you are on a nearly deserted highway.

I have an uncle that drives a 94? civic vx and gets nearly 70mpg when he drives across canada by tucking in behind transfer trucks. I wouldn't recommend this though either, as you have to get in pretty close to see any effect, and some truckers don't appreciate it very much.

Some tires have low rolling resistance... again there is often a trade off here, either with treadwear or with handling... Also while picking out a tire, lighter tires require less energy to rotate, and taller tires require fewer rotations to travel the same speed, which requires less fuel, but reduce your off-the-line performance.

A/c does save gas by reducing the air resistance but only at highway speeds... Around town, its better to roll the windows down... from a mileage perspective.

Parking in the shade and using those windshield shades will prevent some gas going to waste to cool our cars...
 

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I have found that the best speed for greatest mpg is between 50-60mpg with the cruise control on! Also i have found using 99 ron unleaded seems to be more fuel efficient than 95 ron unleaded.

Plus if you can remeber high school physics,(without being too sad) Kinetic energy is proportion to the mass of the vehicle and its speed squared! E=.5mv^2. So if you reduce your weight by getting rid of rubbish in your trunk or your back seats or kids etc and slow down you should have decent mpgs.
 

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last trip back from Detroit

257 miles, 5.3 gallons, just over 48 mpg.

Not as good as my 53 mpg last year, but that was with a stock DX tranny, this was with the close ratio "race tranny", rear bumper cover still inplace, and wider tires. Plus I also had the bigger Crane cam this time.

3200 rpms, 65 mph, 13-15" of vacuum on my map, "boner magic chip2" with 22-23 BTDC base timing, about 48 degrees overall @ 12 in/mg.

Time for a attempt at 55-60 mpg :)

Damn I love my D15Beast7 :)

I was also hauling two trannys
 

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what octane are you using? I just installed a vac/boost gauge. At lower speeds and once you've reached X speed you can dictate the vacuum, but not all the time, which is obvious I'm guessing anyway. trying to understand what your talking about. Is 13-15 * ideal or is it more of what part of the map i increase the timing. Like I would say my cruise rpms/when I shift is about 2k-3k. So if I just increase that column to like 45* the vac wouldn't matter??
 
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