Calculate your mileage for the most accuracy. Instead of extrapolating miles per tank of gas.

Divide miles driven by gallons consumed. Keep a notepad in your glovebox. Takes all of 30 seconds to record it when you fill up with gas.

Any consistent drop (don't assume anything in 1 sample) tells you that your engine is not running at the efficiency it used to run at.

 

That's what I do

 

I'd say I get the worst mileage out of all of you.

300km's per tank, which I believe is 75litres.

I don't remember all my specs, but, it hurts.