Computer MPG calculation?

[dougb]

Ok, so I've only got 1200 miles on mine, and I'm watching the MPG, one of the reasons I bought the car.

My computer says I'm getting an average of 38.5mpg. When I "do the math" at the gas pump, I'm "only" getting about 35.6mpg.

I've heard (read) about others mentioning the computer is about 3mpg off. Anybody else seeing the same?

[trbasil]

Don't know, in almost 3 years of owning a MINI I have never used the onboard computer to calculate the millage. There is just the common consensus that it's off, and it's easy enough to figure it up the old fashion way that I never bother to spend the time to reset the computer each time.

[miniguru]

The computer on the car is just a guesstament. I've sold a bunch of customers the Scangauge II to calculate mileage. Because you can correct it for wheel and tire size, number of gallons you put in the tank and a bunch of other things.

[fastlane]

My car always calculates/estimates about 2 or 3 mpg better than reality also. Like trbasil, I always hand-calculate anyway.

Curiously, my speedometer is off by a fair amount as well. I think I remember reading that it's pretty common (maybe over on NAM?). I'm about 4 or 5 mph off up around 70-80 mph according to two different gps units that I've had in the car. My guess is that the odometer is off a bit too.

[kylej]

I noticed my car reads 5% high on the speed as well. Confirmed it with my GPS.

I haven't been paying as much attention to the MPG as I am the total at the pump each time I fill up.

[miniguru]

Yes your speedo is prob. off. BMW builds this in to decrease speeding tickets, and in Europe they can be severly fined if the speedo is off the other way in which you are going faster than it says.
I don't even use the car's speedo anymore. I programmed the scangauge and use it when driving from Indy to Atlanta. It takes me about 30min less to get to Atl. using the accurate speedo.

[BKMini]

I have found the speedo is off compared to my Garmin.
I am going to ask D&R when I am there the next time.
I don't think for a car coming from Europe should be off that much.
One more thing, I think the cup holders need to be redesigned, especially for a coolly.

[dougb]

I've got 26k miles on my MINI now.

My speedometer reads about 1 mph faster than my Garmin. My MPG is still reading about 2 or 3 mpg than my "math" calculations at the gas pump.

I'm getting between 36 and 37 mpg, on average.

I drive mostly highway miles, about 150 miles per day, right at the posted speed limits. Too many police on the roads I drive to speed. I see an average of three police cars every day driving home from work. They camp out on Hwy 37 around Bloomington.

My drive two work consists of about 40 mile (flat) drive at 60mph, then 25 mile (hilly and lots of turns) drive at 50mph.

[minidiver]

Cars coming from Europe will always read 1% to 3% faster than you are actually going. The way the law is there if you are going faster than it reads there is a VERY large fine. So, all the companies err on the side of caution.

[minidiver]

If you want a completely accurate speed and gas mileage, just Call Way and get the ScanGauge II. That way you can have those figures up in front of you all the time along with other readings of your choice. And you adjust the accuracy of those figures easily any time you change tires and when you fill the tank. I keep water temp and intake air temp up on mine. If I didn't have a boost gauge I would keep manifold pressure up on the display.

[Professor Zoom]

I found that in almost every MINI I drive the speedo is around 2 to 3 mph higher than what the GPS is saying... this is understandable with the number of speed cameras in England... as far as I know I (knock on wood) didn't get a violation while there. When it comes to gas mileage after four years the obc is a good guesstimate. I bought an app for my iPhone and it was pretty close to what the obc said, then again I have a rather heavy foot.