BMW Mini Gets Worse Gas Mileage After Oil Change



2004 Mini Cooper. I just took it for an oil change at Pep Boys and my wife says the mileage has dropped from 30 to 22. Tires are fine. Used synth oil. Otherwise runs ok. Any ideas?


Just a guess, is it possible that some sensor connection was knocked off during the oil change? Is your check engine light on?


It’s just as much Chrysler as it is BMW. If you use the A/C it will cut into the mileage, especially on cars with smaller engines. Also I think you’re supposed to use 91 octane for the best mileage and best performance with this particular car. You can also try having the computer read and see if it has any stored codes.



But Craig is correct. The only likely explanation is a vacuum or electrical connector being amiss.


Absolutely, the 1.6L engine in the Mini was desgined by Chrysler and what was left of Rover. It was built in Brazil.


Very interesting! You need a scorecard to keep track of automotive pedigrees these days.


Maybe they overfilled the oil. That would cause the crankshaft to waste energy churning the oil.


Maybe they overfilled the oil. That would cause the crankshaft to waste energy churning the oil.

And can damage the engine. Check that one out before you drive it again.


I agree with the others . . . it has to be something else . . . a sensor . . . a vacuum hose . . . something was disturbed while the tech was doing the oil change. Why don’t you re-trace the steps or procedures of the oil change, and see where your hands go, looking for loose connections at these points of the engine? FoDaddy has some interesting points about the A/C, the computer codes and the octane, maybe combined would cause a 30% drop in mpg. Wouldn’t a knocked off sensor or vacuum hose come up on code when reading the computer? Rocketman


It is not unheard of that Hydraulic lifters change immediately after an oil change. However, that also results in valve tapping. and I’m not sure it woudl result in this great a change.

I’d look for somethign disconnected, sensor, tube, etc. first.


I understand this engine was developed as a joint project with Mitsubishi, Chrysler, and Renault?? as a World Engine to be built at various locatiosn, the Chrysler one being built in Sao Paulo, Brazil.


Just want to thank everyone for posting their suggestions. It turns out that Pep Boys dramatically overfilled the oil. It was 3 inches above where it should have been on the dip stick. It was not a happy experience at Pep Boys. I went back this morning. It took over an hour at 8.15 am. I could see the car mechanic talking on his cell phone while posing to work on the car. The Pep Boys manager didn’t care when I complained. The Pep Boys clerk then remarked like they were doing me a favor and not charging me for another oil change. I was the one losing money by having to come back and miss work. Not even coffee available.


Yup, stay away from all those types of places. Document this issue just in case you have any related engine problems in the future. Don’t sign any type of waivers.

Find a good independent shop (maybe a BMW specialist) and use them for routine maintenance.


Nice call, circuitsmith!

FSK, make sure you let Pep Boys corporate know of your “satisfaction.”


You might want to check your transmission fluid as well. They may have made a Jiffy Lube mistake and drained your tranny fluid and over filled the oil.
Some may chide me for this, but I’d just use the dealership for your oil changes from now on. It’s likely there’s a BMW showroom on the same lot as the Minis, so you’ll likely get the same service you’d get as if you bought a BMW(technically you did, but hey…) and they’ll want you to keep coming back and should treat you fairly reasonable.


How far did you drive this car before finding out you were overfilled? (long enough to make a mileage calculation) how far was it? Makes you want to check these things after service,sounds like a good practice Wonder where the tech got his capacity spec? any idea how much (in volume) the engine was overfilled. You are taught to always pull the stick and check the level. Since it was synth oil the tech just kept opening bottles and pouring. Terrible job performanceJust a thought how many quarts of oil were you charged for? They dont give this stuff away. How was the tech able to get more oil from inventory than you were charged for and more than your car called for. I dont believe Pep Boys has a overhead dispenser for sync oil. To easy to steal from.