Is topping off the fuel tank bad for your Prius?

I don't know about the pumps where you live (or maybe it has something to do with living at 7,000 ft?) ... I frequently encounter pumps that click off VERY prematurely, without any doubt.

In other words, what counts as "topping off"?

If the tank accepts over a gallon more by restarting, to me that doesn't seem like topping off.

 

That's true...if the underground tanks are full the pumps really go fast. I usually let the thing fill on the "fast" mark then, when within a few gallons of full, I switch it to the "slow" fill and wait for the auto stop.

 

It's sure not like it used to be. The old way of knowing a cars tank was full was when gas ran down the quarter panel or shot out of the fill hole behind the rear license plate.

 

The very same topic came up here not long ago. The short answer is that filling the tank that full causes damage. That degree of overfill normally takes at least about two gallons after the pump shuts off. Significantly lower amounts might not cause damage. Use common sense. Sometimes I add 1.5 gallons, but only if I won't be leaving the car parked on a warm day before burning off at least half a gallon. That has not caused problems.

 

The only way to know is to get the diagram of the fill pipe and it's assorted secondary tubes, than locate by looking at the filler tube where the breather tubes are on the specific model prii you own.

 

I've topped up every tank since 2012 without incident.

Your charcoal may vary

 

Fill until it shuts off. Wait a few seconds, pump slowly until it shuts off. That’s all I’ve ever done. Sometimes full speed pumping causes a backwash that shuts off the pump (good), but so long as you aren’t pulling the nozzle out to go higher than that, you should be fine.