Originally Posted by Masteratarms93
And how hard is MPGs to calculate? Fill up your tank, reset your trip meter. When the tanks after you put an exhaust on last longer than they did before you apparently improved your MPGs.
If you're trying to tell the difference between 10 MPG and 20 MPG, that will work, but if you need precision, then first, you need to fill the tank exactly the same way both times, perhaps using the same pump handle (some pumps will put a little more gas in than others). It also won't work if you have one
leg of a trip on it that involved either an elevation change or prevailing winds.
It's better if you keep track over multiple tanks. So do 10 tanks of gas and divide by the total mileage over that period.
When y'all put bigger tires on do you re-calibrate your odometers? If not, that will make it seem like you're getting lower gas mileage than you really are. Hit the trip button when you drive past a mile marker on the interstate and see if you're rolling past another in 10 miles as the clock rolls to 10.0. If not, then make a note of what it says, and you've got a conversion factor for future reference. If you go from a 28" tire to a 31" tire, you'll cover 10% more distance with each turn of the tire, but the odometer won't know it.