My 04 Cooper S is only getting about 29 mpg on a mostly highway commute. Has anybody else experienced this, or have any ideas what could be causing this poor milage?
The tire pressures are correct. I change the oil at regular intervals. It's even got a new air filter. According to the specs, a 2004 Cooper S should get 25 city/34 hwy. My highway speed is pretty consistent at 65 mph.

 

That might be a little low, especially if you're driving at 65 MPH.

Just for comparison, my '06 MCSc averages 26.5 MPG with 50/50 hwy/city driving with average speed in the mid 30s. The best was 27.8 MPG. I've never done a full highway drive for any one tank.

 

How are you figuring the mileage ? Hard number crunching or are you relying on the computer display ?


IMO if you are hard crunching the numbers 29mpg is pretty damned good, especially in mixed driving.

 

Bill,

How many miles on your MINI? I have 73k on my '06 MCSC and have noticed the fuel economy dropping off a bit in the last few months. I'm just about due for "Inspection II" on the OBC, so I'll be replacing plugs, wires, and the supercharger drive belt in the next few weeks along with all the other filters. I'll be curious if it helps.

 

I think you are getting about the right MPG.
If you do research, you will find that the government numbers are usually off by a few MPG. Also the goverment tests are done with 100% pure, undiluted gas...not the E-10 that is sold today....this is responsible for another couple MPG....
Add to the fact you must be running the AC in VA, and a bit of engine wear....and 28 is a good number....
I was averging about 28-30 on my MINI, bone stock before I modded it....the tune, pulley, etc...and I am still getting 27-28, with a lot more power!!
You may have a pulley or other performance part and not know it too....you might also look at the octane gas you run....higher, the better...lower octane results in retarded timing, as does hot air form heat soaking on a hot day, the IC just gets hot, and cannot keep up at slower speeds (sounds like VA again), and you really need 93 octane if you have a pulley....91 is fine for stock on a cool day, bit if you have a pulley, the timing WILL be retated with 91.
Also the tire brand/size will affect MPG...High performance tires usually have high rolling resistance=LOWER MPG....as does heavy rims/tires....
Non standard sizes of tires make the speedo inaccurate...so you might not be getting accurate mpg calculations....and the on board computer is notoriously inaccurate...so do the old miles/gallons=at fill-up.

 

Thanks for all the replies, everyone.
Some of you mentioned "hard number crunching". I've been using the onboard trip computer, which I reset at each fill-up. Is it more accurate to go with the regular odometer? I wouldn't have thought there would be a difference there... Interestingly, my Garmin GPS trip computer indicates slightly more miles completed at fill-up that my onboard trip computer.

The fact that I live in Virginia Beach with the heat and humidity and therefore constant AC use must be having some adverse affect on mpg. It will be interesting to see how much the figures differ in the winter.

I have no mods on my ride, yet, although I've been pondering the pulley change. Only 42k miles on it so far, but racking up quickly with the commute to my new job. I use only 93 octane. Stock rims on 16in tires. Using non-runflats now.

 

One other thing to consider is that some parts of the country are now permitting more than a 10% level of ethanol at the pump. If you live in one of those places you can expect to see your mileage suffer.

 

That does seem a little low. The OBC on my '02 tends to read 2-3 mpg high so your actual might only be 25 or 26. That is definitely low. How's the air pressure in the tires? Maybe jack up each corner and rotate the wheels to make sure brakes aren't dragging. Run some Redline SI-1 fuel system cleaner through a tank.

I have 80k miles on my '02. With a pulley, intake, and exhaust, I hit over 40 mpg on the highway (OBC reading) on a mostly highway trip (55-65 mph). Cruising at 70, I average around 33 or 34 with A/C.

 

My '03 MCS rarely if ever averaged over 30 mpg, most of the time it was closer to 26-28...........I don't think 29 mpg is poor, and I wouldn't worry about it. You didn't buy it for mileage, you bought it for it's looks and driveability, the mileage is a bonus - so drive it and enjoy it!

Those who say they can average 40 in an MCS, sorry, I don't believe you, unless you're just going downhill!

 

I've never been able to get above about 32 mpg, but as others have stated, the amount of ethanol in your car, coupled with running the a/c will impact your mileage. may also be time for new plugs. i think the manual is overly optimistic on plug longevity, at least for having the car run in peak condition.

 

The computer is usually optimistic by about 1-2 mpg's. Gas mileage should be figured the old fashioned way.

 

I live in Florida, no hills around here. This pic was taken towards the end of a 120 mile journey from Orlando to Jacksonville. Today was actually the first time I've seen over 40 mpg indicated on a longer highway trip, normally it's on slower 50-55 mph roads.

Still, I too, have heard of many people having a hard time managing over 30 mpg. If it's been like that since day 1, it's probably driving style. If you notice a sudden change that you can't account for (I definitely notice a difference between summer and winter gas blends), then you should look more into it.

 

I think the sweet spot for MPG is around 50 mph, which is why I probably do better around town than on the highway

 

I was looking at some related links.
Back in 2008 they adjusted the method for calculating the fuel figures for all vehicles. This website allows you to see what your car should get based on the newer method: http://www.fueleconomy.gov/feg/ratings2008.shtml

1st gen MCS figures at 25 city/31 hwy.
My last tank got 30 mpg after I boosted the tires to 33 psi and watched how I accelerated.

True, I didn't buy my Mini for the fuel efficiency - I bought it because it's fun. My concern was that there was something wrong with the engine. After reading many of your comments and the website above, I'm pretty sure that my Mini is where it should be.

Whoever thinks they're averaging 40 mpg, pass the bong to me!

 

I go with the odometer reading and divide by the number of gallons in a full tank (as soon as the red gas light comes on). I get to drive from Orange County to San Francisco on the 5 Freeway so I get some pretty good averages. As a lot of you know, the 5 is as flat and straight as California highways get.

I only get around 30 mpg going around 75 mph. That's all highway, no stops unless I need to pull over to use the restroom.

Mixed, I get about 21 mpg. But I drive almost all city miles. I consider LA stop-and-go traffic to be considered city, FYI.

 

+ 1, a good week for me is 27 MPG and i do mostly highway driving between 65 and 70 MPH.

 

Well, i just wacked off the pre-cat and after two full tanks of my same exact drive PLUS an auto-x, i have seen a 2mpg increase in MPG. Take it for what its worth.

 

Can somebody translate that into layman's terms?

 

Had my stock '02 MCS for 8 months now and have pretty much only run around town and to work (2 miles) with it and I get ~27 mpg consistantly. Last weekend my wife took it to a class reunion out of state so I reset the computer before she left. She drove from upstate NY to central PA, a lot of mountain driving, ran around town all weekend and back to NY. The computer said she got over 35 mpg for over 500 miles of driving. I figure it was actually about 34 mpg if you hard crunched it because I have noticed ~ 1 mpg difference when I've check it in the past.

'02 Liquid Yellow MCS

 

He removed the 1st catalytic converter....the Pre-cat.
The main cat, the one that does most of the emissions treatment is the 2nd one.

 

As others have said, the OBC tends to read high (usually by a couple by sometimes more), so it and hand-calculated numbers really aren't comparable.

I doubt very many are getting consistent, true (not OBC) 30+ mpg on stock Gen1 cars. Since new on my 2004, I've gotten 28-30 on trips and 21-23 in mixed surburban/urban driving. This is more/less normal from what I hear and more-or-less consistent with the revised/more-realistic EPA numbers which are 22/31 (combined 25). 29 mpg OBC on a mostly-highway commute sounds exactly normal to me.

Gen1 cars, for their size, are no mileage champs. Relatively poor mileage is a big reason Mini ditched further development of the supercharged Tritec and went with the much more efficient turbocharged Prince engine in the Gen2 cars. Mini's also, Gen1 or Gen2, have pretty crappy aerodynamics.

- Mark