[Nailloren]

Average fuel consumption = Test mileage/ Total gallons of gasoline used during the test period
Let us use the following as an example:

Initial mileage is = 24,500mi
Final mileage is = 25,000mi

Test Mileage = (25,000-24,500)
Test Mileage = 500mi

I conducted this test for a 7-day period

Day 1 = 1 gallons
Day 2 = 2 gallons
Day 3 = 4 gallons
Day 4 = 3 gallons
Day 5 = 4 gallons
Day 6 = 2 gallons
Day 7 = 4 gallons

Total test gallons = ( 1 + 2 + 4 + 3 + 4 +2 +4)

Total test gallons = 20 gallons

Average fuel consumption = Test mileage/ Total Test gallons

Average fuel consumption = 500mi/20gallons

Average fuel consumption = 25miles/gallon

How do I know if this calculated average fuel consumption is right, is there an additional yardstick I could leverage?

 

[blowboat2001]

I just fill my tank and record the mileage. When I next fill my tank I just divide the miles driven by the fuel added. And if you have an 04-07 CTS-V with only 25k miles, there are people in the CTS-V Facebook groups who would buy it!

 

[AAIIIC]

I conducted this test for a 7-day period

Day 1 = 1 gallons
Day 2 = 2 gallons
Day 3 = 4 gallons
Day 4 = 3 gallons
Day 5 = 4 gallons
Day 6 = 2 gallons
Day 7 = 4 gallons

What "test" did you conduct? How did you measure the fuel consumed? How did you manage to end up burning exactly whole gallons for 7 days straight?

Average fuel consumption = Test mileage/ Total Test gallons

Average fuel consumption = 500mi/20gallons

Average fuel consumption = 25miles/gallon

How do I know if this calculated average fuel consumption is right, is there an additional yardstick I could leverage?

I don't understand what your question is. You are correct, MPG is simply the miles driven divided by the fuel burned. Assuming you measure those two numbers accurately, the calculated average fuel consumption is right. How could it not be? 🤷‍♂️

 

[PhilD]

I keep track -- but only so if I notice that the mpg is way off all of a sudden, it's a good indicator that something is wrong.

I get an average of 16 in the CTS-V so it's not something I wanna be reminded of My Escalade isn't much better

 

[Pereira]

@Nailloren
If I get you right you are trying to be sure that your vehicle’s fuel consumption rate is normal and not unusually high. If this is the case you can make a comparison with the data provided by fueleconomy.gov which is readily available on every car's window sticker.

The window sticker also known as the Monroney sticker can be generated from Detailed Vehicle History and or Monroney Label, either way, you could find a reasonable yardstick for comparison.