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Originally Posted by kamsmart
Drove 540 miles with still two pips left on the fuel guage in the MFD. MFD read 64.5 (with only the last 450 miles tracked .. I had cleared the MPG reading when the ODO reading was about 110 miles). Apparently, I must have done real bad on the first 110 miles, since the pump MPG number that I calculated was about 55 MPG.
I know that there might be some discrepancy in the values that MFD displays and the number at the pump .. but this is too big a difference ..
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The bladder in the Prius tank is not as 'deterministic' as ordinary tanks. You can get considerable variation in each tank but over time, the errors average out. These variations can be as much as a gallon.
Feel free to take a peek at
my mileage chart to see how bad it can be. Last week's top-off was not enough to reset my fuel indicator and looked like 3.3 gal. for 208 miles, 62 MPG. All weekend, I drove around with an indicated 60% full, according to the fuel gage. Then Sunday evening, I topped off and put in 3.4 gal for 108.0 miles,
32 MPG. Then I remembered the variable fuel tank.
What probably happened is the tank had a bubble large enough for about 1 gallon of gas in the first fill-up. So it didn't really fill up the tank which explains why the fuel gage never reset. Then when I filled up Sunday night, the 'bubble' was gone and an extra gallon went into the tank. When you add both tanks and miles together, 6.7 gal and 316 miles, the mileage comes in closer to the expected 50 MPG (I had used the AC on a couple of very hot trips.)
Bob Wilson