I’ve done two full tanks comparing mileage from trip odometer/math vs. the MPG computer. My MPG Gauge is very accurate, to within a decimal place.
RE: MY MPG GAUGE IS VERY ACCURATE
Post by tjts1 » Mon Jul 13, 2009 10:52 am
VCA wrote:
matthew1 wrote:I’ve done two full tanks comparing mileage from trip odometer/math vs. the MPG computer. It’s accurate to within a decimal place.…and it will be, unless your fuel level sender goes ape, thinks “empty” occurs when you have 3 gallons left and starts throwing trouble codes
No. The trip computer doesn’t use the fuel level sender to calculate MPG. It uses injector pulse width vs speed. The car was designed to show empty at 3 gallons. When the tank is that low, you can starve the fuel pump in sharp turns. Its a safety feature. The reason fuel pumps die is because owners repeatedly keep driving after the low fuel light comes on.
RE: MY MPG GAUGE IS VERY ACCURATE
Post by VCA » Mon Jul 13, 2009 7:23 pmtjts1 wrote:No. The trip computer doesn’t use the fuel level sender to calculate MPG. It uses injector pulse width vs speed. The car was designed to show empty at 3 gallons. When the tank is that low, you can starve the fuel pump in sharp turns. Its a safety feature. The reason fuel pumps die is because owners repeatedly keep driving after the low fuel light comes on. Might be true on the 850s, but on the networked cars (post-99), the long-term fuel economy is reconciled with the fuel level difference over the last 100km. Otherwise, ECM-4050/DIM-0002 gets thrown and the trip computer (I assume) errs on the side of the lower figure. I know this because of the 6 months of throwing that code on my car and being 2+ MPG off (using the same gas pump and computing mileage between tanks). Replacing the sender made the figure agree with the computed economy
. Oddly, the ECM is capable of throwing that code even if you don’t have trip computer software installed.
Last Updated on April 7, 2022
