Ive looked under refueling and cant find ..not top off..

I'm not sure if the 2008 Owners Manual is identicle to the 2007, but in my manual I find it in Section 2-1 "Operation of Instruments and Controls", in the subsection titled "Fuel tank cap", which begins on page 48, and continues with the following warning on page 49:

 

Interestingly, the warning indicates the possiblilty of fuel splashing out, but it makes no mention of damaging the EVAP system, or effects on warranty coverage. Perhaps there is another warning I'm less familiar with? Anyone?

 

While hairgal shouldn't be expected to read a Toyota Technical Training manual, here's what it says about overfilling:

 

Not topping off has been good advice since the early 80's when charcoal cannisters became standard equipment on US autos. Prius is no different, except the consequences are more expensive due to fuel getting between the bladder and the tank shell. Leave the pump on slow, auto shutoff. When its done, hang it up. If the pump fails to shut off, contact the station owner when you have a repair estimate. Most have insurance to protect them. Usually this is used for things like water that may be pumped from their storage tanks into your vehicle, but it won't hurt to try. Bring another car to the same pump nozzle and see if it shuts off automatically.

 

I would be very surprised that your mileage took a hit from an overfill. I can see damage to the evap system, which causes a DTC to be logged, but in general that shouldn't make your mileage worse.

Don't let the dealer con you. That said, most mileage drops are simply changes in driving conditions. How long have you been driving your Prius? Have there been any recent changes in your driving habits, traffic, temperature, road conditions, etc.?

Tom

 

I am wondering what is your method to determine that your mpg dropped; and what is the amount of the decrease?

It sounds like you are only on your second tank of gas, perhaps this is too soon to come to a conclusion about a permanent mpg change?

If you have no warning lights on, there should be no damage. In that case I doubt that the dealer tech will do much for you.

 

Like Patrick says you really need more (about 4) tanks to calculate the mpg by dividing the miles traveled/gallons pumped.

If, after this averaging out, your mpg is below 40 you might want to see if it improves following the initial break-in period.

You might want to find a flat piece of land to drive 100 miles on cruise control at 60mph and come back and tell us what your MFD says. Also note that A/C can reduce your mpg sigificantly especially in city driving.

Your complaint of too low an mpg reading is almost invariably every new owner's "issue" with the car.

 

Topping off is bad for ALL emissions controlled vehicles, not just the Prius.

 

Did you reset your consumption screen when you filled up? If you didn't you are seeing the lifetime mpg and not the tank mpg.