wanted to apologize first for another mpg thread, but i wanted to see about my exact situation and mods.

with the mods that my car have, and when i try and not drive like a speed racer, i still only manage to get about 260-270ish miles out my 03 MSC....usually about 11 gallons, give or take.
car is at pretty much exactly 80K miles now

i was thinking now that i have smaller wheels it would go up, but not the case (17s to 15s). even in summertime, i never have the AC on...

most of my driving now is on the highway at about 70mph (at almost exactly 3k RPM)....i try not to go over it on highway as im not in a hurry. 65 or so seems too slow for around here and it would drive me mad too hehe

most would say get free flowing intake and free flowing exhuast, look at your plugs, but i have all that hehe, just cleaned the foam ALTA filter not long ago.

im thinking maybe fuel filter?( would that really make any difference?)
02 sensors (been reading about that as well as it seems that comp takes that in consideration till they fail, so not sure anymore?),
maybe get different plugs (i have colder plugs couse of the 15% pulley).
i JUST changed the belt to NAPA one as suggested here for 15%...
i ran some injector cleaner a while back, as well as seafoam...

im baffled....while it gets better mpgs than other cars, i think that it should be more than about 25ish?

any suggestions anyone?

 

check out pure gas.org maybe someone in your area sells ethanol free

 

my '05 is stock and the trip computer tells me my fuel economy is 25mpg with 90% city driving. It lies in first gear, putting the clutch in at 15mph and I'm getting ~50mpg, at 10 I'm getting 35, and before it shuts off under 5mph, I'm getting even less mpg. Which begs the question, do I really get 8mpg at red line in first gear?
the total mileage estimate after a tank of sunoco's 93 (which is E5 in new england) shows a distance of about 325 miles I think.

 

Driving style, the DT bypass valve, and tire/wheel choice (diameter, width, and rolling resistance) are all major contributors to mpg..octane of the fuel too...
I get 30+ with my mods on the highway driveing at 72...much more it drops off fast...at 68 I can get maybe 2 more mpg, but it is not keeping up with traffic.
The DT bypass valve will reduce mpg...Just a fact, but you get boost at lower rpm's, so you get a sportier ride...
Tire choice...both rim weight, tire width, and rolling resistance affects you by about 2-3 mpg...narrower tends to roll better, wider handle better, both winter or summer tires tend to be more sticky...so higher rolling resistance...
You driving style is the biggest contributed to mpg...along with traffic...

 

Also, ethonol fuel has less btu's per gallon...so lower mpg's...as a side mote the EPA allows car companys to do mpg test with pure gas...no ethonol!!
If you have auto temp control..try turning off the ac..it runs most of the time, like when the defroster is selected...even if not needed!! That is good for another 1 mpg or so...

 

Also, measure mpg's the correct way - filling up and dividing the miles by the gallons for the fill up. Measuring by "X miles per tankful" is highly inaccurate and can vary widely.

 

The trip computer tends to be a bit optimistic...by 1-3%
also if you rims are a non-standard diameter...that throws all the calculations off...You can develop a bit of a correction factor using the % differance between you speed on a gps and odometer...you need to apply it to your miles traveled and if you want avg speed, that too!!

 

thx for the replys...
the tires are properly inflated 195s, so not wide at all.
i dont have a trip meter, so i use the simple ol' miles traveled per gallon, so thats what i get.
i filled up the tank w some chevron today, and got a fuel filter that i will tackle soon, so we will see if that does anything.

 

yup, so fresh fuel filter is in....well see if it does anything...but i reckon it cant hurt

 

is that your old fuel filter on the right, or your oil filter?

 

toilet filter looks like haha

 

I changed the fuel filter in my old car once. it took one look at my rusted rocker panel and didn't want to be left out so it developed a hole for itself.
Funny how rich the thing ran after that and I had to clear the ECU...

 

yeah mine threw a 300 code i think, random missfire on all cylinders, i cleared the ECU via the reset button on dash, restarted it, cleared the code and its all good.
seems to be running a bit smoother, since i did the filter, fuel injection, and cleaned the air filter.
well see...

 

I've been cursed with the same problem, only worse. My stock R53 gets 20-21 mpg, not much difference between city and highway and I don't drive like a maniac either. Like you I checked the plugs, tire pressure, changed the oil and filter, air filter. It also passed the smog check with flying colors and seems to run as well as any car I've ever owned. Because of this it gets little driving time these days as I use my '94 Integra for my daily driver. It's not as fun to drive as the Mini but gets MUCH better mpg.

 

One thing...highway to most folks means cruise set, or steady speed for long periods of time...last time inwas in LA it was constant speed changes due to traffic...not very good for mpg.
On a 2 hr trip where I touch the brakes only 2 or 3 times is almost always 30+...
like said before octane affects mpg...and it was found by dr O that a car with a 15% pulley on ca gas will always having the timing retarted a bit..when this happens, the car enrichens the mixture too...

 

Any improvement with the new fuel filter?

 

seems about the same last time i checked. i actually sold the car shortly after, but didnt seem to affect mpg that much. ran a bit smoother tho, i must admit.