MPG sensor accuracy?
 

Since I got my 07 Sport, I've been getting average mpg consistently around or above 17 mpg in city driving, and around 19-21 highway.

The other day I was on the expressway going about 55, and I had it in 4WD due to the weather and never changed it back to 2WD when I got on the highway. I looked at my computer and it was telling me my average mpg was around 23, and it even went up to 25.5! Should I trust this, or is it some type of glitch? I had just reset it after a fillup. I'm running Revo's in the stock size.

Usually when I fill up the computer says my range is in the higher mid 300's, like 365, 360, etc.

I'm realizing the math isn't working out, but when I do notice the numbers that's what they usually say. :)

I'm mostly wondering if it is possible to actually get that mpg in 4WD.

no, its a glitch...your mpg is a calculation thats rarely excactly :smokin: correct. would be nice though!:smokin:

The fuel economy indicator is only as accurate as the odometer and whatever data the computer uses to calculate fuel usage.

If you are reading instantaneous MPG and not average MPG, you will find times when the MPG reads high during periods of reduced engine loads (downhill, tailwind, etc.). So the times you read higher MPG may not be a glitch.

I don't think there's any kind of fuel flow meter to calculate actual fuel flow or consumption. The computer would have to be able to estimate fuel consumption based on air flow, ambient temperature, coolant temperature, etc. (the same data the computer uses to control fuel mixture), and then make a MPG calculation based on how many miles are driven over a period of time.

If the fuel mixture is accurate, the fuel usage calculation should be accurate. As long as the odometer is also accurate, the MPG indicator is probably pretty close to correct.

To check it, it would be a good idea to use a GPS to check odometer accuracy. Then you would fill up, reset the MPG indicator and trip odometer, and divide how many gallons used per tank into how many miles driven per tank.

Do this for several tanks, using the GPS milage information to correct any odometer inaccuracy. Compare this to the accumulated MPG average for all of those tanks (or you can do it tank by tank).

I think you'll find that the fuel economy averaged out over a whole tank or several tanks will be fairly accurate.

The computer on my 2003 V8 4Runner is usually at least 2 mpg optimistic. Use your trip odometer and divide miles driven by the number of gallons you pump in. The computer display is just not accurate.

mpg
 

Mine is about 5 mpg optimistic, maybe it doesn't know about the supercharger

Mine was about 2mpg high with the stock tires, its about 1.5 high with the one size larger Revos... IMHO, the only thing sorta right on that computer is the outside temp.

I've driven 50miles after the "range" hit zero and still had 1.2gal left in the tank.

I hope they just get rid of it on the 2009... and add the 5.7 (if Toyota is reading).