Checking True Gas Mileage

[JAG ReDDoG]

Hello,Ive got a 2008 GMC Sierra sle 5.3 which i think has a 29 or 28 gallon tank.I finally let it get to the point where the low on fuel light comes on.The fuel gauge level is maybe a 1/2 inch above the empty mark on dead left.I know when the light comes on you usually have a gallon or 2 left.Roughly how many gallons are left at this point?I understand its not exact but close maybe.

 

Ive gotten 438 miles at this point before the light came on on a tank.I feel good about mileage even thou its only got 2458 miles on the truck.Along with a KN airfilter and thats it.

 

Im reading alot of you guys experiences with wheatly tunes ect hoping to get a tune pcm in the future.Everything ive read seems positive as far as the tune goes.I hope to pickup maybe 1-2 mpg after the tune.

 

Thanks everyone for your thoughts.

[Lincoln30]

Isn't it a 26 gallon tank??? When the light comes on my truck I have at least 4 gallons left in the tank.

[Bostonsfavson]

Yes, our tanks are 26 gallon. I assume all the GMT900s are the same, but I'm not sure.

[Zembonez]

Mine comes on when I have 3 gallons almost exactly. 2.9 at last check or 51 miles to empty on the DIC. If yours is about the same with a 26 gallon tank, the fuel mileags should be something near 19 MPG which is beyond what most of us get. Your method isn't scientific enough to yield real results. Just fill it up at that point and calculate your mileage. Pretty simple.

[JAG ReDDoG]

Ok the 26 gallons makes alot more sense.Still thats good overall i think.BTW thanks for your replys.The dash computer shows 16..9 average overall.

[iminaquagmire]

Its really not good to run it down so low. The fuel pump is cooled by the fuel in the tank. Try to keep at least 1/4 tank at all times.

[unit731]

Its really not good to run it down so low. The fuel pump is cooled by the fuel in the tank. Try to keep at least 1/4 tank at all times.

 

 

True.

 

I've never had a fuel pump fail. But I usually keep 1/2 or more in tank.