I drive a 2004 S with 98k miles on it and the gas mileage has gone to crap now. I calculated it and it is around 22mpg. What's the issue? I just drove from Orlando to Destin FL (about 336 mi) so the mpg should be great

 

When was the last tune up, plugs and wires, air filter cleaning or change? What speed were you traveling? Also did you to it today in the horrible wind and rain we have been having in Florida?

 

same issue i was gonna post something too.

before the winter i was able to get 375 miles out of a tank and willing to put money i could get over 400 if i didnt drive it so hard. and thats doing a constant 85 with the AC on full blast

now i can barely get 330. what gives i though maybe it was just winter gas but there has got to be something else up. and this was before i got my new rims and tires.

 

and the distances dont lie i know becasue i did a trip from my house to my grandmotheres that is 70miles so 140 there and back, then again my house to my sister inlaws house that it 85miles another 170, then from school and back. thats 70.

140+170+70= 380 on one tank and i still had plenty left. enough to probably get over 400 so i dont know whats going on with my car that i cant get over 330

 

I need to join this, almost the same issue

 

Hey greek, you just did a boatload of work, right? Maybe you need to keep your foot out of it. Keep it under 70 with cruz on. LOL

 

yea but no mods to the engine/drivetrain lol so im not really pushing it just to hear it or have fun. and believe me i have tried to baby it i still can get the mileage i got before the winter came. beside its spring now so every tom, richard ( its funny nam edited the name d1ck) and harry is out with there sports car and is cloggin up the highway. so im only limited to 70-75 lol

 

Have any of you tried resetting the adaptations?

 

I wish I could see 400 a tank. Pure highway I get about 300 before the low fuel light which means I am filling about 11 gallons..27 mpg and I consider that a good day. I know the tank holds 13.9 but I really don't like stretching it. According to:

http://www.fuelly.com/car/mini/cooper%20s

I am on the high side for a 2003 cooper s

 

yea i have tried resetting the ECU does nothing for my mpg. you know it doesnt make sense to me the distance i have traveled in my car is proof i have gotten 375-380 out of a tank.

maybe a fresh oil change and some seafoam will help out.

 

Greek...new tires can make about 2-3 mpg diff....more rubber on a tire = more rolling resistance....then add a grippy highperformance brand....maybe wider...will hurt too....as does HEAVY rims that folks get cause they are cheap..even if they are the same size. If the diameter of the new tire/rim combo is different...that affects both gearing andthe odometer/speedo.....wider tires though are a huge mpg killer in a mini...but more grip...so a trade off.

 

i understand that. but what im saying is i was getting bad mpg before i switched to new rims/tires. so no changes and i get bad mpg thats what im talking about.

 

A lot has to do with driving style.....i can get 32 mpg if i drive nice...low 20s if i rev it up....i know if run my motor above 3000-3200 rpm on the highway, i loose mpg pretty fast....
So from a mpg perspective, i run 71.....heck faster is fun, but $$ in my pocket in exchange for a 2 minutes long drive lets me have more fun......better places to use my $$ that the gas stations.
the mini is no honda when it comes to mph.....heck a sc car must be run rich....and in the summer, higher intake temps mean richer to prevent detonation. Not sure what to tell you.
Pure highway, i can get 28-32, or 25 mixed....22 having a bit of fun, even less with traffic..
.less if you have wider than 195 (stock s width) tires or have a lead foot.

 

I haven't changed anything- driving style wheels tires oil changes no mods. The only work I have done was install an ATI crank pulley because the original was going. This bad fuel mileage has just been happening. Could it be the MAP air sensor? My exhaust has been really wet lately, it drips like every 20 seconds

 

You are correct about the tires, when I got my 05 S they had Pirellis runcrap and got rid of them as soon as I could and went to DSW's before the change I was getting up to 34 on the highway stock everything 26 combined, then After the new tires and one ball mod my MPG went south 20 to 22 combined per pen and paper calculations at the same time it's fair on the highway I just try to keep it under 3k rpms, I recently switched to a drop in K&N filter so let's see how that goes.
I recently made a trip from NYC to Salem,MA then to West Hatford,CT and my low fuel light came on getting close to Wallingford CT, I left with a full fresh full tank and although I forgot to note the mileage I think that that's about 350 miles or a bit more of highway only with maybe 5 total city driving. I did drive it pretty fast on the way to MA mostly 80's but on the way back I was doing mostly 65,70 ish so I don't know I guess the tires are to blame a bit low rolling resistant better for that but hard to come by.

 

I guess my gas milage is near normal. Durring the week I have lots of straight flat freeway on the commute. Trip computer shows 28ish. By the weekend, I put some twisties between me and my errands, cause I live in the country kinda. Trip computer quickly falls to 27 after a spirited trip. Filled up, and 26.19 mpg combined by own and paper.

Wanted to ask Zippy, do wider tires bring milage down because the foot print is bigger, or because larger typically weighs more?

Right now I have the S-Lights, 17x7 and we all know they're heavy, around 25lbs if I remember right. I saw some 17x17.5 that are 16 lbs, would that likely increase or decrease gas milage??

 

spark plugs?

i was having same issue with my r56, i changed air filter (which wasn't that bad, but still, it's cheap) and spark plugs, it seems like solved for me now.

i dunno man, if someone says "i'm having worse mileage than before", i think saying "don't give too much throttle" is not the right thing to say, i mean they probably can remember their driving behaviours, right? but ofc, it still can be cold weather, crosswinds, tyre pressure etc.

 

It was great weather on my drive back to destin and I noticed the terrible gas mileage a week or two before that. City driving i get 17 MPG in a freaking 1.6L engine. This is not right at all. It used to be around 30 combined city/highway. I am not just racing around everywhere........

 

Throwing any computer codes? I'm thinking O2 sensors affect fuel mix. Any vacuum leaks? I think whoever already said spark plugs and air filter was on the right track. Make sure maintenance/tune up items are up to date, then trouble shoot

Let us know what it turns out to be

 

Yeah....how many miles? The o2 sensor could be getting weak/slow...
sudden changes are usually an indication of a change....mpg does typically drop a bit SLOWLY as a car ages....just not suddenly.

 

Not sure which makes more of an effect...
but generally lighter rims allow faster acceleration, the side effect is lower fuel burn, and imo nicer handling. Light rims on a mini, imo, just feel right....a side effect to the easier/lower force turning seems to be longer ps pump life (lower load on a dc motor, so it kinda makes sense).
The narrower contact patch from a narrower tire is certainly a mpg gainer...imo it comes down to how you drive, and how YOU use the car....pick the right width....a very wide tire has tons of grip, tends to hydroplane, does poorly in snow....
frankly i found the 195 on an s is pleanty for me....i think most folks, unless they track a car, never really understand the true limits of a mini....
heck...i just picked up a set of 15'srimd cheap...tossed some 185 width tires i plan on using this winter since my snows only have half a season left....think with the same outside diameter i gained about 1.5 mpg with a grand touring 15 vs a uhp 16...not quite enough grip for the twisties, ok, but should be fine for when i will be running them.
the selection of low-rolling resistance performance tires are slim...most are pretty basic tires...so not much of an option there.
but i think good basic mx is the biggest thing...
good plugs, clean filter/oil, healty motor, and decent o2 sensor...they have a life of about 100,000 miles, and do get slow to respond....and hood driving habits are the biggest things.

 

Good stuff above here.
Wider tires have more rolling resistance and also less aero, plus a little weight. All bad for FE.
If the plugs and air filter are good then look to the o2 sensor. Dirty injectors could also be a factor. Another possibility is the wheels being unaligned.

 

Good advice above.

Like everyone said , plugs, wires, and air filter changed or still good, the next suspect is the O2 sensor. Also, If you have not changed wheels or got new heavy tires.

I have noticed in the past the gas mileage dropping on multiple MINIs and just did the tune up a couple miles before. Miles drops then after a while you will the the CEL. Then read the code: Bank 1 or Bank 2 and its the 02 sensor. One goes then the other.
Since you are around 100,000 time to change. I got near 110,000 out of mine in the past.

One pre cat and one post cat. Same part number.

http://www.ecstuning.com/Search/11780872674/ES27122/





Good luck and I hope you can narrow it down, but sounds like O2 to me.

 

I hate to say it OP, but I take mileage as the single most important high-level indicator of the health of my car, so I think you are very wise to take note.

Many good ideas are offered here, to which I would only add that for me the second most important indicator is compression and leak-down testing.

If you get decent numbers that are balanced across the cylinders then you can breath a sigh of relief knowing you've a mechanically healthy Mini and go find out what the damned nuisance component is that is messing with your efficiency.

Cheers,

Charlie

 

One thing that has not been mentioned....
if the change is sudden, a dragging caliper is possible....
Simplest way to check is go for a couple mile drive, minimal braking....then park...and feel the heat comming from the rotors areas....fronts should be about the sameleft to right, and rears similar...
if one is MUCH hotter...you have a sticky brake.