Originally Posted by DrkKnight614
More often then not the read out on the dash changes due to conditions and will give you what your car is averaging at that moment. Its not necessarily what you average will be after a full tank, like what the other equation will dictate. Granted neither of these are 100% accurate.
Where do you get this information from? I've been figuring gas mileage since my dad would yell at me for not figuring it fast enough using long division and a pencil and paper,lol. If you reset the mileage when you fill up and run a full tank before resetting again it will give you the mileage for that tank, not at the moment. I have checked it manually and by using the car computer on my 2005 GMC Sierra, 2008 Mustang and 2003 Freightliner and they have all been very close. I would say in terms of accuracy percentage the vehicle computer is probably closer to 100% than figuring it manually. Although, neither is perfect.