Bad mileage, bad gas, car computer adjusted??

[J_w73]

ok.. I've had my car for about a month and put almost 3000 miles on it.. (I know.. YUCK!!)
Anyway.. I have been averaging about 51-54 mpg through a tank according to the MFD. When I calculate by miles driven and how much gas I put in it seems to be around what the mfd says or alittle better..( I know this is inaccurate with the fuel bladder being in these cars).
Anyway, my last fill up at Shell I reset the mpg and did my drive to work. I noticed the mpg being low and it being difficult to achieve the higher mpg stretches. The weather was really really windy and rainy that day so I just attributed it to that.. Well I just got through the rest of the tank and it didn't get any better..I was about 42 mpg with 3 pips left and the gas mileage started to get better as it usually does with less fuel in the tank (lighter car / higher mpg??) Today I had 1 pip left so I decided to fill up. The final MFD mpg was 47.1... going 360 miles..(I normally get around 450 miles on a tank) When I computed it with the gas I put in (8.7 gallons- seams to be around the norm) it came out to 42 mpg.

Just drove my normal route home on the fresh tank (no Shell gas) and got a record 61.1 mpg on the MFD. Best before that was 54 mpg.

Questions and facts..
The Shell station sold E85 gas also.. I didn't use the E85 hose but is it possible they put E85 in the wrong tank either on purpose or mistake?

If so, will the computer adjust the performance of the engine based on the power/energy of the fuel..?

Would this explain my average mpg going from 42 -47 mpg in less than 100 miles or my 61.1 mpg on my ride home with the new tank?

I would say the outside temperature was a little colder than normal during that tank.. nothing extreme though.. around 55-65 instead of 65 - 80..
on the drive home it was around 79...

[qbee42]

Cold weather and fuel formulations could easily account for your mileage variation.

Tom

[uart]

"The Shell station sold E85 gas also.. I didn't use the E85 hose but is it possible they put E85 in the wrong tank either on purpose or mistake?"

Very interesting. Maybe you should try a tank of E85 in it some time just to see if it gives you the same low MPG as that last tank. I'd be indterested to know the results anyway.

[F8L]

The really windy and wet day basically screwed up your tank. Because it is an average of your total MPG for that one tank you cannot overcome driving in such conditions unless you started hypermiling to artifically inflate the numbers left on that tank to get close to your normal average.

[JimboPalmer]

Originally Posted by uart

Maybe you should try a tank of E85 in it some time just to see if it gives you the same low MPG as that last tank. I'd be indterested to know the results anyway.

The Prius is NOT a flex fuel car. I would not do this.

[philobeddoe]

i hope this isn't too off topic, but i am modding my gen ii to run on hazelnut oil and bald eagle heads

[uart]

Originally Posted by JimboPalmer

The Prius is NOT a flex fuel car. I would not do this.

Hi Jim, does E85 refer to 15% ethanol or (yikes) 85% ?

We don't have E85 in Australia, I think I wrongly assumed that must have been 15% ethanol when it's really 85% ethanol. Is that right?

[JimboPalmer]

Originally Posted by uart

Hi Jim, does E85 refer to 15% ethanol or (yikes) 85% ?

We don't have E85 in Australia, I think I wrongly assumed that must have been 15% ethanol when it's really 85% ethanol. Is that right?

Yes, E85 is 85% Ethanol, 15% gasoline (petrol)
It would only have 70% of the energy of pure gas, so would get less MPG, but the plastic parts of the car would need to be designed for Ethanol, as it may be a solvent to materials in the fuel system.

Most cars in the US run fine on E10. (10% Ethanol)

[J_w73]

Originally Posted by JimboPalmer

The Prius is NOT a flex fuel car. I would not do this.

Thanks for that info...

[J_w73]

Originally Posted by F8L

The really windy and wet day basically screwed up your tank. Because it is an average of your total MPG for that one tank you cannot overcome driving in such conditions unless you started hypermiling to artifically inflate the numbers left on that tank to get close to your normal average.

so why the 61.1 mpg on my trip home with the fresh tank??

I have never averaged that much on a trip to or from work..