[Obioban]

A while back I compiled some data for a project I'm working on. Since this seems to be coming up a lot more recently, I thought I'd post it and some fuel efficiency tips.



Explanation of what's above:
-I had a 3 mile highway course, which I ran both directions (6 miles total). I marked one direction as "there" and the other direction "back" (this was only supposed to be for me, I wasn't exactly formal about it ) If I had to slow down for a car, etc, I redid the run. "There" was more uphill than "back"
-The highway had both hills and curves, so the below in no way represents optimal fuel economy for the car.
-except for the side columns of "AC on" and "windows open", all runs were done with the windows up and the AC off
-All runs in the "there", "back", and "avg" columns were done by setting the cruise control to that speed to take me out of the equation
-data was pulled from OBC and speedo-- aka, it's not real speed or fuel economy. That said, it is the speed you'll see and it's still accurately showing us relative fuel economy
-all runs done in mexico

Analysis of the data:
- The optimal speed for fuel economy in this car seems to be around 80mph. This is actually great, as, at least in my experience, that's where traffic cruises most of the time
- Having the windows down uses MORE gas than the AC, at least at highway speed. AC only uses 1.2 mpg at 90mph, while having the windows dow uses 5.2 MPG! (at 90mph)
- a well trained foot gets about 3mpg better than the cruise control at any given speed (and that's without traffic fuel saving techniques)


Fuel saving techniques:

1) If possible, never use the brakes. Any time you're in gear and not on the gas pedal you are getting virtually infinite mpg. To that end:
-never tailgate-- it forces you to use the brake pedal. No amount of "drafting" is going to make up for that
-the moment you see a red light, get off the gas and coast. You're not going to get to the destination faster by getting to the red light faster
-DO NOT TAKE THE CAR OUT OF GEAR WHEN YOU'RE SLOWING DOWN. Leave it in gear until your RPMs are around 1400, then put it in neutral. You're not using ANY gas at all if you're off the gas and in gear

2) Prepare the car properly
-Low tires pressures will cost you fuel economy. I run 36psi (cold)
- keep your car as light as possible- don't keep your crap in it.
- a bad alignment can also destroy fuel economy-- especially too much toe!

3) Mods can hurt fuel economy too
- gears mean your using more fuel at any speed
-wider tires are worse as they create more rolling resistance
-many power mods lose mpg
-any software that increases throttle sensitivity is going to make you more likely to be on the gas more
-exhaust are likely going to make you want to be in the wrong gear-- the drone zone is pretty optimal for fuel economy

4) General techniques:
-as much as possible accelerate on the downhill and coast on the uphill. Be willing to lose some speed going up hill, but no so much as to require a downshift
- use as little throttle as possible. WOT uses much more gas then edging up to speed
- higher gears are always better (but don't lug the engine). 6th gear pretty much all the time on the highway
- never use the brakes if you can help it!
-when accelerating, get into the next gear as soon as you can without lugging the engine. By 40mph you can easily be in 4th gear.
- don't use cruise control, so long as you're actually able to do the above. I got 3mpg better on the highway with my foot than with cruise control, and that didn't even include ANY traffic, traffic lights, etc-- just wide open straight road that I had to myself)

5) Don't skimp on the octane: You will get lower MPG with lower octane gas. High octane gas pays for itself, don't skimp!



None of the above means you need to drive slowly. I averaged 29.4mpg driving home from the beach today, a 180 mile drive home. I also averaged 82mph (average-- meaning I was going 102 for every moment I went 62) and the traffic on the road was not insignificant (obviously no traffic jams, though)-- so it's not like I was driving like a granny. That drive was also only in mexico

[TheSt|G]

Someone was booking it.

[Obioban]

Originally Posted by TheSt|G

Someone was booking it.

Yes... but economically

[yaja23]

Excellent info, thanks for sharing

[omega3651]

After driving from NC to Philly and back I was averaging 420 miles to a tank. I also found that even cruising at 80 mph (in Mexico of course ) that I was actually getting very good gas milage. My average speed for the trip was 85 mph...( you smart guys will figure out my true speed ).
You might be right about the cruise control finding as I do not have cruise control in my M3. It kinda sucks driving hundreds of miles without cruise but those long stretches without traffic make it all worthwhile.

All in all the M3 makes a great highway cruiser, if you wanna sight see.

It also has the ability to go from MD to NC in 5hrs on one tank of gas.

[rwfisher]

considering i do 82 miles a day....

Oh yeah, getting stuck in traffic REALLY eats the gas. I went from 25-27 MPG on a wide open interstate to <15MPG while stuck in traffic......if possible try to time your trip to miss the backups.....

[Obioban]

Originally Posted by rwfisher

considering i do 82 miles a day....

Oh yeah, getting stuck in traffic REALLY eats the gas. I went from 25-27 MPG on a wide open interstate to <15MPG while stuck in traffic......if possible try to time your trip to miss the backups.....

CBs are also great for avoiding traffic (and cops)-- the truckers tell you about both before you get to them

[rwfisher]

Originally Posted by Obioban

CBs are also great for avoiding traffic (and cops)-- the truckers tell you about both before you get to them

+1...used to keep one in my MR2. Also useful for coordinating with the big rigs to minimize folks who like to cut into line.....

[pourfood]

I had a chart similar to that for my TSX back in 2004 and I was able to achieve better than average MPG than most of the people so I don't think I'm a "noob" when it comes to minimizing fuel consumption as much as possible, but honestly..the best I got with pure highway cruising with my M was 21. How more than 25+ is achieved with this car is beyond me.

I just had my inspection II done as well and on the commute back home (40 miles) the computer read 20.5, which in reality is about 19MPG, so I don't think it has anything to do with my filters, tire pressure (I check regularly), or driving habits...huh.

Also doesn't this car have a rating of 16/22 ?? (Not that it's 100% accurate)

[Obioban]

Originally Posted by m3isffej

I had a chart similar to that for my TSX back in 2004 and I was able to achieve better than average MPG than most of the people so I don't think I'm a "noob" when it comes to minimizing fuel consumption as much as possible, but honestly..the best I got with pure highway cruising with my M was 21. How more than 25+ is achieved with this car is beyond me.

I just had my inspection II done as well and on the commute back home (40 miles) the computer read 20.5, which in reality is about 19MPG, so I don't think it has anything to do with my filters, tire pressure (I check regularly), or my lead foot. Huh.....

Maybe an issue with your coils? Some members said their economy went up by 5mpg after having them replaced