Great MPG
03-02-09, 06:18 AM
#7
"Ultra" or "mid grade" gas doesn't have ANYTHING to do with MPG. It is the ability of the gas to resist detonation under pressure. When the gas ignites prematurely (before the piston is in the correct position), the engine will "knock." Most modern engines can detect this condition and adjust the fuel/air ratio to compensate.
My guess is that really high MPG results come, in part, from the amount of gas which is filled. If I'm waiting for the wife to use the gas station bathroom, I can often squeeze in at least an extra half gallon or even more after the tank is initially full. Really "topping off" would reduce the MPG calculation for the previous miles, but make the next fill-up MPG seem great.
My guess is that really high MPG results come, in part, from the amount of gas which is filled. If I'm waiting for the wife to use the gas station bathroom, I can often squeeze in at least an extra half gallon or even more after the tank is initially full. Really "topping off" would reduce the MPG calculation for the previous miles, but make the next fill-up MPG seem great.
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03-02-09, 07:42 AM
#8
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Mpg can't be accurately calculated on one fill up, as there are too many variables. Any change in the slope of the ground at the station drastically affects what a "full tank" means. Ambient temperature and the accuracy of the pump meter are other variables.
03-02-09, 06:23 PM
#9
"Ultra" or "mid grade" gas doesn't have ANYTHING to do with MPG. It is the ability of the gas to resist detonation under pressure. When the gas ignites prematurely (before the piston is in the correct position), the engine will "knock." Most modern engines can detect this condition and adjust the fuel/air ratio to compensate.
My guess is that really high MPG results come, in part, from the amount of gas which is filled. If I'm waiting for the wife to use the gas station bathroom, I can often squeeze in at least an extra half gallon or even more after the tank is initially full. Really "topping off" would reduce the MPG calculation for the previous miles, but make the next fill-up MPG seem great.
My guess is that really high MPG results come, in part, from the amount of gas which is filled. If I'm waiting for the wife to use the gas station bathroom, I can often squeeze in at least an extra half gallon or even more after the tank is initially full. Really "topping off" would reduce the MPG calculation for the previous miles, but make the next fill-up MPG seem great.
I generally do not top off when I refuel. Also, I use both the on board trip computer and a standard calculator to figure the MPG for these long road trips. Pretty sure 25+ mpg was what I got on trips in NC and GA as well as a different road trip in FL and AL.
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