Fuel Mileage/Distance to Empty Question

[NickB]

I've got a 2007 GMC Sierra 4WD NBS

 

i do mostly in town driving and i get about 11-12mpg (distance to empty on full tank 320km)

 

my question though is if i reset my avg fuel economy and fill my tank, drive on the highway and get my avg fuel economy to 16-17mpg should'nt my distance to empty increase? after a fill up with the avg mileage reading 16.7mpg it still tells me the same distance to empty as when my avg reading was 11.4.

 

i feel as if i should be able to get more than 320km to a tank of fuel or am i wrong?

 

others ive talked to with similar trucks are getting 700km to a tank? (obviously on the highway but still a big difference)

[newdude]

Do you consistently get 11-12 mpg? If so, the comupter knows your driving habits and projects your mileage/km to empty based on your driving habits. If you short trip alot, it will probably remain consistent. If you always averaged a higher mpg, then the range would reflect that.

[Doug_Scott]

Just because it says 320km does not mean it will only go that far. I am pretty sure that in my truck (2010 Sierra) the range number is live to current consumption. I can get into the truck that has been running in city only for last week or so, see that I have 300km range, get on the highway for 30km and the range will show I have 310km range. Also fairly certain that if I get in the truck, check the range to empty, then reset the average mpg, the range does not reset, it stays where it was at. The longer you drive the vehicle in a way that is different to what the average was before reset will be reflected in range to empty, but in an average sort of way. In other words if you are currently getting 20mpg, the range applies that to the history of the previous readings.

 

Take the reading with a grain of salt, it is not telling you what you will get, it is saying you may be able to go that distance. Have to wonder where it is getting the amount of fuel that is in the tank. Fuel gauge is not really accurate enough to count on for computing distance to empty with any certainty. If gauge is off my 10%, that can be 40 miles in distance to empty. Long ways to find out it was not 100% accurate.

[93gmc$$]

Don't know why you are mixing Miles and KMs, but anyway. If the system is working the distance to empty (range) uses the fuel gage sender to calculate fuel remaining and divides that by the AVG MPG reading. If you want to see if it is working, try this. Coast down a hill at 50-60 MPH or so. Your instantaneous MPG is a big number, then bring up the distance to empty and check the number, then reset the AVG MPG. If everything is working the RANGE should go to a real big number while you are idling down a hill.

[greg74]

11-12 mpg sounds a bit low considering your truck appears to be completely stock, even if it is almost all in town driving. My 99 Z71 has a leveling kit and 33's on it and I estimate 14-15 mpg. I'm assuming your truck has a 20 gallon tank, I think that's what mine has, with 320 km being right at 200 miles. I think I can probably get around 475 km or just under 300 miles if I were to top off and try to run until empty, probably a safer estimate would be about 450 km. I think it probably takes several tanks to get your computer to think you're going to get better fuel economy, its going by past knowledge and estimating future economy. It probably just lazily remembers your previous mileage and by measuring how much fuel is in the tank, it calculates from there. Its probably going to be more accurate by simply watching the fuel gage along with your trip odometer. That's what I have to do anyway since my truck doesn't have the option to tell me my fuel range.