Thread: 50 mpg!
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Old 02-14-2010, 07:37 PM   #26 (permalink)
bestclimb
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Join Date: Oct 2009
Location: South Central AK
Posts: 933

escort - '99 ford escort sport
90 day: 42.38 mpg (US)

scoobaru - '02 Subaru Forester s
90 day: 28.65 mpg (US)
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Quote:
Originally Posted by busypaws View Post
Don't forget that gas weights a little over 6lbs per gallon. So if you are always driving around with 10 gallons of unused fuel (filling every time) then you might get a percent or two better on a trip with an empty tank. (Only if stop/go, EOC, P&G; If you're in cruise control then weight is not as much a factor.)

The extra weight (60 lbs or 3% of a 2000lb gross weight vehicle) is only a determent when stop and go. EOC, P&G, and steady speed it likely won't drop much. The extra weight may take more energy to accelerate but once it is up to speed the extra kinetic energy you have and/or potential energy you stored will allow your coasts back down to be a bit longer. If you have to accelerate the extra mass then use brake to decelerate it again you will see a drop in MPG.

I think the error in tank fill by <.2 gallons per fill by using different stations, weather conditions, or individual pumps, or alignment of the planets gets pretty well washed out by averaging a couple tank fulls. That said I usually fill up at the same station, but that's mostly due to convenience.

400 miles/9.3 43.010 M/G
400 miles/9.1 43.956 M/G
which is about a 2% error.
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