Now that I have 3,000 miles on my Mini, and have kept pretty detailed logs, I've found that the speedometer error is about 5-6% and the OBC fuel mileage error is also 5-6%. Both in the same direction. Odometer error is less than 1%.

It appears that the OBC uses the speed to compute the MPG, is that the case?

Since everything runs through the OBC is there any way to correct it? I found what appears to be a menu for that in the OBC but haven't yet tried to mess with it, if it is even accessable.

Any ideas?

 

Don't sweat the small stuff.

 

sweating the small stuff means that your warranty will expire before its time..

 

My Speedo and MPG are both within 1%... Verified via GPS and running @ 60mph on flat, straight road for 1 mile (in as nearly as 1 min. exact as I can measure)... did you change tire /wheel size or brands?

Also changing injectors will affect MPG calc. (but not speedo)

 

odo = 1% off.... 1% of 36000 miles = 360 miles. I do 30 miles each day that means warranty will expire 12 days quicker....no biggie.

 

Nope the car reads it differently so you can keep those 12 days. And GPS is more prone to error than most realize. There was a thread that covered this in great detail not to long ago.

 

I'm not too concerned with the odometer. But if there is an easy fix to get the speedometer and MPG estimates down to where they really are that would be nice. I've checked the odometer against the GPS & interstate mile markers and found that it reads 100 miles when both the GPS and mile markers read 99.4, close enough. But the Speedo reads 75 when I'm really going 70.5 to 71 and the MPG on the OBC says 34.5 when the trusty pen and paper vs. mileage says 32.5. Small stuff? Maybe, but irritating nonetheless.

By the way, the car is bone stock mechanically.

 

look at it this way, you are less likely to get a ticket since you are going slower than you really think you are. Of coarse this also means that more cars are passing you when you think you are going the correct speed.

I wonder if MINI does not make adjustments based on wheel size. I have the 16s and drove past a speed trap thing and noticed I was going 32 instead of the posted 35, and where my speedo was stating 35.

Are you on 16's, 15's or 17's? Since all of those can be delivered tire sizes, but I wonder if the car is set for 1's, or if there is something with the British conversion that wasn't quite correct.

 

Wheel and tire size variations are sure to be part of these variations from vehicle to vehicle. I focus on the road ahead! Motor on! Have fun!

 

I went in but didn't have the memory or the guts to do anything so I went back out.
On my previous BMW, I calibrated the OBC so that it gave the same MPG number as my manual calculation down to +/- 0.2 mpg. I pumped gas from the same pump for about 5 tanks to get that calibration that accurate.
Here is the instructions on how to do it on a BMW. http://home.iae.nl/users/bts/obc.htm IIRC, my MCS also has 21 items. So .. 19 is probably to unlock.
Here is the corrections to the list.http://www.bimmer.info/forum/showthr...ight=obc+codes
It says #7 is not % fuel remaining but the actual number of liters remaining.
Any explorers out there to try it on the MINI?

Another site http://www.bmwtips.com/tipsntricks/t...ring528OBC.htm

 

Oh... to get to OBC....
1. put the key in.
2. push the start button and hold the right stalk on the tachometer until something pops up....