Odd MPG goings on?
#1
Odd MPG goings on?
Has anyone noticed that their MPG numbers go dramatically downward as you reach the end of the tank?
I don't have enough evidence to support my theory yet, but it appears that everything is fine and dandy with MPG until the gas gauge drops below the 1/2 mark. Then, no matter what I do to increase the MPG figure from that point to the 1/4 mark and lower, I keep *losing* MPG instead.
If this really is true, then that means inorder to maintain MPG numbers, I will need to fill up at 1/2 tank, which doesn't make a lot of sense to me. Anyone else's input?
I don't have enough evidence to support my theory yet, but it appears that everything is fine and dandy with MPG until the gas gauge drops below the 1/2 mark. Then, no matter what I do to increase the MPG figure from that point to the 1/4 mark and lower, I keep *losing* MPG instead.
If this really is true, then that means inorder to maintain MPG numbers, I will need to fill up at 1/2 tank, which doesn't make a lot of sense to me. Anyone else's input?
#2
Re: Odd MPG goings on?
I notice similar effects in my 05HCH. My theory is that as the tank passes the 1/2 way point, the computer accumulates more data points. More data points = more accurate results. If you don't reset the trip/MPG odo each time you fill up, you will notice a more stable MPG reading with time. When I first fill up my tank and reset the trip odo, I notice mpg reading anywhere from 50-70mpg.
If you have an A/B trip odo/MPG meter, try keeping one of them on long term without resetting it each time and the MPG data will eventually smooth out.
If you have an A/B trip odo/MPG meter, try keeping one of them on long term without resetting it each time and the MPG data will eventually smooth out.
#3
Re: Odd MPG goings on?
Ralph is right. The computer is making approximations.
The only way to accurately calculate a change in MPG per tank is to use the number at the gas pump. Even if your odometer reads higher or lower, your % change in MPG will be accurate.
Just recently my HiHy read 40.4 mpg over the first 10 miles after fill-up. I can assure you that at my next fill up, my calculated mpg will be around my usual 21mpg.
The only way to accurately calculate a change in MPG per tank is to use the number at the gas pump. Even if your odometer reads higher or lower, your % change in MPG will be accurate.
Just recently my HiHy read 40.4 mpg over the first 10 miles after fill-up. I can assure you that at my next fill up, my calculated mpg will be around my usual 21mpg.
#4
Re: Odd MPG goings on?
I've observed the same thing - the computer "average" clearly drops about 1 - 1.5 mpg from the first half to the second half of the tank. I've been getting 400+ miles from each tank, and even on a long trip in same conditions I'll observe this phenomena. It doesn't bother me - I record my mileage using hand calculation, not the computer - and my overall average mileage has been very consistent. It must have something to do with the starting point or assumptions the computer uses for it's averaging.
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spiff72
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06-26-2009 08:54 PM