i'm only getting 19 mpg in town. i've checked tire pressure, cleaned the air filter, reset ecu procedure, and it got to 20 mpg. i know there is an exhaust leak but i cant find it, i smell it, i think its in the flex section of the header....but my real question is...will an exhaust leak cause that much of a mpg loss? in the 3 years ive had the 03 mcs, the city mpg has average 25 mpg. ive only put 6k on the car since i bought it( dd, but a small town) the only mod is a pulley and borla catback that was on it when i bought it.

 

My first guess would be the exhaust leak is messing with the oxygen sensors. Sometimes extra air comes in through the hole, and they read oxygen values that are off the charts. Other times exhaust leaks out and that throws it off. Or extra air coming in combusts unburned fuel in the header and that plays hell with what the ECU is expecting to read. It could be so bad that you're in limp home mode.

Seems like finding a take-off stock header for cheap (or free) should be easy, since so many cars have aftermarket ones. I'd fix that and see what it does.

I'm only guessing since I don't know how many miles are on the car, if it's throwing any codes, where you drive, the weather, or your driving style. But yeah, an exhaust leak could hit your mileage.

 

^^Ditto^^

The O2 sensors are what control your fuel mixture during normal driving (Not WOT). Therefore an exhaust leak could definitely throw things off.

 

My 2003 Cooper S gets around 20-21 MPG around town and has done that for years. That is 'real" MPG, not computer MPG, which is a few MPG higher. There are no issues with my car and part of my low MPG is due to our high (10%) ethanol addition in Washington state. The high MPG claims on this forum for Gen 1 cars is amazing and I don't understand the wide variation in figures.

 

How's your alignment? Do you run wider, stickier tires? Could you have a brake caliper dragging? Is your check engine light on? Are you often stuck in traffic? Do you drive with a heavy foot? How's your maintenance upkeep?

There's a lot of things that can influence gas mileage. I'd start with your driving habits since you say it's all in town driving. And repair and maintenance work, obviously.


Gas mileage is definitely influenced by how heavy you drive on the gas pedal. People who baby their cars around are going to see much better mileage.

It's an extremely example, but on the track an AP1 S2000 gets under 10mpg. On the way to the track it gets around 22mpg.

 

all very good points, it was mentioned to me at work last night that the switch to winter gas here in oregon will affect mpg. but affect 3-4 mpg kinda suprises me.

i would say my maintenance practices border on obsesive, crazy, almost.

ive got 140k miles, no codes

thanks for all the inputs, gives me alot to think about.

there are alot of ebay/amazon cheap(er) headers without cat, but the o2 sensor placement seems off on all of them, i like the price.

 

oh and my driving style is consistant, thats why i noticed the mpg change.

 

I've heard the winter gas makes a difference, could be why my truck is hanging just above single digits for mpg the past few weeks...

I would start with the exhaust. Then pull the wheels, lubricate your caliper pins, and check the condition of your wheels bearings. You can even just raise each side of the car and give the wheels a spin. if a caliper is stuck or a bearing is going, it should be readily apparent.

Do you let your car warm up? I know I went from 13mpg-ish to 10mpg-ish in the truck when it got cold and I was letting it idle before I left the house.

 

19mpg in town isn't horrible. Now that other guy a while back who said he was getting 12-13 mpg in town....now that's horrible!!

I get around 20mpg if I do only in town driving....and anywhere from 25-27mpg on the highway.

Also, realize that in the colder months...you car will run richer to compensate for the colder/denser air....so it's going to use a little more fuel.

 

Ive noticed mine has gone down a bit also. But it's wintertime and they use that crappy winter mix blend around here.

 

The Milltek header is a good one, with a robust cat and properly placed
O2 sensor, but about as pricey as the OEM one (usually slightly over $1K).

 

My MPG varies quite a bit for no apparent reason to me. I drive almost entirely in the city and I do have a consistent driving style, yet sometimes I'll get 20-21MPG, and other times I'll get 24-25MPG. On the highway I seem to hit 28MPG pretty consistently. And yes, these are hand-calculated mileages. I've read other threads where people claim to get 35MPG highway in their R53's, I think that is absolutely nutty. My dad is lucky to get 30 in his R50.

 

I see about 21 to 22 MPG pretty consistently on my almost all stock 2004 R53 JCW. This is hand calculated.


Does anyone know how to calibrate the MPG displayed on the navigation system trip computer? This thing consistently reads about 30 percent high. I've read how to do it on a Mini that doesn't have navigation system but can't find how to do it on one with the navigation system.

 

I have a 06/R53, the best I've gotten was 27MPG. My R50 got 31-32 max highway. I use premium 93 octane. What you're getting would appear to be the norm. I would question those stating they are getting 30+ in a R53.

 

I've kept track of gas mileage for my 2002 MCS from day one. When I lived in San Francisco I did 20+ road trips to Oregon and SoCal totaling 26,000 miles, on which I averaged 31.6 MPG. On one tank of gas driving only the streets of SF (averaging 15.5 MPH) I got 17 MPG.

 

32 MPG? You lucky duck.

 

2002 Mini Cooper 'S' - 135,000 miles
I think I posted something like this a few months ago.
Tank-to-tank calculations are not really meaningful; even the dash-board readout uses some level of history, maybe the previous 1,000 miles or 3 or 4 fill-ups. Below are my records since last August - miles between fills & mpg for each tank.
Lowest I've ever seen is 23.5, highest 30.5 - I don't do much city driving.
The overall average is 26.82mpg.

347 30.19
324 29.14
327 27.59
333 30.49
360 28.96
354 29.93
344 27.52
348 27.72
334 27.81
340 27.23
303 27.63
351 26.82
233 26.14
307 26.67
292 27.10
300 24.67

Mike