I've got an '06 MCS and my gas mileage has gone from about 24mpg to 18mpg for the last two tanks. I installed a M7 cooler thurmostat last summer and a Stratmosphere exhaust a few weeks ago. The car seems to run fine. I live in central Florida where the temperature has been in the low 30s for over a week. I haven't been driving more than about 6 miles to work or to the store. My thoughts are that the ECU is running the rich map since the car never really get to warm up. I may also be keeping the revs a little higher to hear the new exhaust. Does this make sence? Any other ideas on my poor mileage?

 

is your scanguage or something telling you this? its prolly is because you want to hear that exhaust, i just got the alta exhaust on mine... and i went through 3/4 tank in 2 days staying local ahaha. enjoy it and then take it easy. hopefully nuthing is wrong.

 

That is not too bad....the cooler thermostat might be dropping your mileage a bit....but not enough to make a huge difference. I bet driving habit are what is causing the MPG...the exhaust should actually +MPG's.

 

I'm thinking this is a temperature related issue as temperatures can cause a fluctuation in MPG pretty easily. Other's may also chime in to say it's 'winter' gas, air pressure change and etc. I think it may a combination of things as the seasons change. I've owned my MINI for about 2 years and I've noticed I get about 17 to 18 MPG in the winter compared to 22 to 24 MPG in the summer.

 

Granted I have the sippier MC but its like clockwork 34+mpg/tank, 95 degress to 15 degrees. Control of your driving habits is 90%. Judging by your short commute, I'm guessing there are several stop/starts. I know listening to my borla exhaust gets addicting but moderation will save mpgs. Assuming you have the 6spd, practice different short shift techniques to see what your fuel does. For example, 1st to 3000rpm to 3rd 2500rpm to 6th. Coast to a stop and judge lights safely. Speed limits, road, and traffic will help determine. Also, sorry to any believers, I think the on board computer is POS at calculating MPGs. I use my gas reciepts mileage/gal. If I compare to the manual capacities, I should be able to do 500mi/tank - which I have... once.

 

[FONT=Arial]Thanks for the response. I’m using the MINI’s tac computer for my mileage reading. I just filled up and will check mileage the old fashion way for comparison. I still have the OME injectors and OME ECU tune. I did install the Detroit Tuned bypass valve last year, which I may remove since it seems to only create boost earlier and waist gas. I’m really thinking it’s mostly the cold weather (with M7 thermostat) causing my 18 MPG as I drive short distances in stop & go traffic. I was getting 24 MPG with the same driving last summer. Finally going to warm up today….we’ll see.[/FONT]

 

Most likely temp related. Car's run richer before they come up to temp. If you've got a cooler Thermostat and lord know's it's been Cold here these past weeks it might not be coming up to temp on your short drive. This would cause it to run richer then normal. Not Mini's but on Volvo's when we get ECT (engine coolant temp) sensor failures they suddenly get terrible gas mileage.
just a thought.

 

this is kinda good to know... i actually did realize a slight change in my MPG since its been a bit chilly here lately. Not a big difference though... maybe having to fill up a day sooner then usual. Stupid gas prices going back up again here in L.A.

 

Sounds like you have all 4 things working against you on mileage

1. short drive of 6 miles, car doesn't get warmed up

2. cooler thermostat, again not letting car warm up

3. DT bypass valve, making boost sooner causing ecu to dump more fuel

4. Generally cooler temps, allowing your car to make a more dense A/F charge buring more fuel

Avoid any or all of the 4 above and I promise your fuel mileage will increase.