1st Gen R53 Cooper S Most liked posts in thread: Terrible fuel economy, any ideas what it could be?

Its Summer and you are driving with a heavier right foot? :devil:

Oh and anything near 30 MPG is great, as for me I am lucky to get 20 MPG.

 

The tires can EASILY be worth 10%+ in mileage, going to a really sticky wide tire from a more conservative one. Also note that (as said) a smaller diameter tire than stock will tell the car it's going more miles than it actually is, reducing indicated mileage.

Also check your trans oil, refill with Redline MTL. That was worth 1.5MPG to mine, and the shifts are buttery smooth. Super easy job, on par with an oil change, but use a GOOD allen wrench and don't bugger up the threads.

Check/replace your upstream oxygen sensor as well, or at least clean it. Made a diff on mine, more drive-able. They can start to "go" without throwing a code, only way to know is seeing the near-real-time "fuel trim" adjustments (of course on our cars the phrase "near real time" is a few times per second, not the dozens of times per second of the newer ones).

 

Hit 31 MPG once, usually it's 30 MPG. It town I'm at 27 MPG. If your tires are smaller in circumference you mileage will be wrong & screw with your calculation for mileage.

Do you have a brake dragging?

 

Feel your brakes/tires/rims for excess heat....
I'm thinking one will be hot from a dragging brake pad.

Edit...saw I the above post you looked at it....
O2 sensors still origina??l....sometimes mpg can take a bit of a dive right before the front one turns on a light....

 

I only get over 30 mpg driving down 81 south going to the Dragon with the cruise control on. Then I get about 400 miles a tank. * note that is all based off the cars computer which is wrong since I have a 15% pulley.

Once I get to Fontana and hit the "FUN" roads I am lucky to see double digits sometimes. I swear I use more fuel and Meth at the Dragon week then I do all year.

 

could be all that drifting you do.
or the huge ego your car has to carry.
Probably the map sensors, Look for a vac leak.

 

Zombie revival.

I recently picked up a new-to-me 06 JCW that was getting an appalling 13L/100kms. It had an exhaust leak at the gasket mating the manifold/cat/downpipe and the exhaust.
After the $10 gasket was replaced, it went back down to the more appropriate 10L/100kms with the same hard driving style (now easily achieving 5.6-7.3 L/100kms if being nice)

 

Check your tire pressure when its warm.

 

I run my wife's same size tires at 35..cold. She also gets crappy mileage, but then, she only drives around 18 mph!:lol:

 

What's the ethanol content in your fuel? Is it possible that you had been using ethanol free and now the stations are using 10% ethanol?

This could explain 3-4mpg.

 

Gas mileage, what's that?

 

dude Firebro! whats up!

 

Hey Colin. Long time no drink!