I have a 2009 FEH with 35k miles and I get from about 29.5 to 31.5 MPG. (according to the standard MPG indicator on the dash) Does anyone know how the vehicle calculates the MPG? Does it use the last 500 miles or 1000 miles in its algorithm? I watch the MPG as much as anything on the dash and I'm just curious what is "under the hood" in this instance.

The '09 FEH has a terrible MPG gauge and reads about 2-3mpg high at around 30mpg. Mine reads ~5mpg high at 60mpg. I've reset my gauge every tank since new and it has always ran high every tank. You have too go by gallons pumped divided miles over about 10 tanks to get a true average. I've gone 884 miles on 13.6 gallons for a true 65mpg tank. The factory MPG gauge read over 70mpg on that tank to give you a idea. I always add as close to 13.6 gallons as possible every tank and almost drain the tank before filling the tank. This is done by going ~55 miles past 0 Miles To Empty.

I'm sure the factory gauge will calculate at least 884 miles the same way every reset in the '09. My '05 FEH would only calculate about 200 miles correctly before it would start dropping older miles and start calculating the new MPG data.

My lifetime MPG can be viewed here by scrolling down at the site:
http://www.cleanmpg.com/index.php?pa...9&viewcar=2612

GaryG

I would say it estimates it by the pulse width on the injectors and does something with how far it's gone how many and how wide those pulses are and figures out what the approximate mileage is, that's how I understand it at least.