99.9 mpg [Archive] - MINI Cooper Forum

: 99.9 mpg

Jun 7th, 2011, 07:23 PM
my mini one diesel sometimes when driving along my OBC reads 99.9 mpg as my current consumption, surely it cant be that economical, then when i fill up again the AVG consumption is around 40 - 50 mpg. also doing 60-70 MPH for 1-2 hours my AVG speed shows 26 MPH.

is my on board computer telling lies or am I missing something here.

Jun 7th, 2011, 07:56 PM
Instantaneous may be that if you have taken your foot off the accelerator and are cruising.

It will soon sort itself out.

Or do you mean your Average MPG sometimes jumps to 99.99 when just normal driving?

Jun 7th, 2011, 08:08 PM
i think it does happen when i take my foot off a bit or even ease up on the pedal, but sometimes it does it when driving exactly the same way without any change in speed.

the average mph thing happens regardless of how I drive, if i'm doing 30-40 mph the avg mph is 12mph

6-70 mph avg speed is 50mph, these journeys are usually 1-2 hours on A roads or motorways.

any one shed some light on this as my warranty finishes soon and if theres a problem, I still have time to get it sorted with warranty company

Jun 8th, 2011, 06:15 AM
When you let off the gas pedal and allow the driveline to pull on the engine (engine braking), the injectors shut off. This happens whether it be a gas engine or diesel. During these moments, the engine uses zero fuel and hence, you see the maximum possible MPG. If you had an air/fuel gauge, you would see the air/fuel ratio go to infinity, meaning amount of air divided by zero fuel equals infinity (high school math).

Jun 8th, 2011, 09:00 AM
If it is happening during normal driving then get it down to the dealer and sort it out under warranty. No point in asking us if you can get it sorted for free.

As for average speed, that will always be low if town driving / start stop at lights. Got mine to 50 mph but that was over a 3 hour drive on motorways having just reset the trip computer.

If you dont reset your trip computer often you will get a much more realsitic MPG value for your car, alternativley make a note of the amount of the amount of fuel when you top up and divide by the mileage to work out MPG