Is the tank completely full ?

The first tank is always suspect. It isn't uncommon for the "full" tank to be somewhat less than full.

Tom

 

http://priuschat.com/forums/other-cars/94001-gas-gauge-says-full-but-thats-not-quite-true-npr.html might be insightful even though it's a Ford engineer talking.

 

When you get gas and the pump clicks off on auto
you can still nurse in another 2 gallons of gas
in the tank until the tank is completely full
with standing gas at the filler nceck.

The real tank capacity is 13.5 gallons or so when
filled in this way...

 

did you have all the pips?

 

It has some fuel before shipping, but is not filled until after it reaches the dealership. Generally a lot attendant takes it to a nearby fuel station as part of the final prep. There is absolutely no control for consistency.

 

Nope; the tank is 11.9 gallons FULL to capacity.

Moreover, it's literally bad for your car to fill the tank up past the click as it can cause damage to evaporation system bits. At least that's what I've read. And it sounds an awful lot like an urban legend, so I tried googling but cannot find anything conclusive either way. I'm in fact inclined to think it's not true, but who knows

 

The only way you would have gotten a fairly accurate figure on fuel mileage when you left the dealer is if you reset the trip odometer and started from there.

 

I remember reading somewhere in this forum that
when filled from nearly empty to the top
of the filler neck it was over 13 gallons.

 

Skoorbmax's point is that 11.9 gallons is the rated gross capacity of the tank. You can exceed the rated capacity by filling the filler tubes and other nooks and crannies, but it is in excess of the rated capacity and may have detrimental effects. Many drivers do it routinely without apparent problems, but every owner's manual that I've read specifically cautions against over-filling.

Tom

 

I remember reading the same thing, multiple times.

But I've also failed, on several attempts, to achieve anything close to that. When trying to pack in extra fuel on long trips where the overfill will be burned off immediately, my filler tube has filled up with less than a third of the 'extra' fuel others have claimed.

 

I have checked the owners manual for our 2010 Prius
and there is nothing stating about filling the tank to the
top of the filler neck.

Perhaps the newer owners manual for the 2011 and 2012
Prius have that mentioned...

 

So as far as everyone knows, filling the tank to the top does not hurt the "so called" evaporation filter or what ever they call it. I would like to see a diagram, or some sort of drawing of what is connected to the filler tube so we can see for our selves.

John

 

I agree, if it was so important the issue would be
certainly addressed in the owners manual.

I know Wayne Gerdes from cleanmpg.com when
conducting his mpg test he fills up to the neck
for consistentency. I don't recall him stating
that this practice will cause severe engine damage.

 

I agree but I still don't over fill. I feel more comfortable not overfilling and when I use to while back before I owned my first Prius it was easy to have gas drip over onto the ground when removing the nozzle.

 

I lost a pip around 54 miles. No way it was full. It's been a while since I drove a rental Prii, but I believe it should go about 125-145 miles before it looses the first pip. I only have 91 miles on my car so I am nowhere near ready to fill her up

Mike

 

The argument I've read is that there is a risk that dirty gasoline might eventually clog up (with residue scum) the gasoline vapor pressure/overflow release valve(s). The arguement continues that inside the fuel tank, there is a fuel pump which pumps the gasoline to the gas engine up front. If the vapor pressure/overflow release valve fails to work properly and gasoline tank experience abnormally high pressure levels then the fuel pump inside fuel tank would experience increase work/stress loads which could cause it to fail prematurely.

 

Basically when you fill the tank, there must be someplace to put the >10 gallons of hydrocarbon-saturated air which is being replaced by liquid fuel. At the highest point of the tank is a vent which is connected to the charcoal canister. The HC-saturated air is fed through the charcoal canister, which adsorbs the HC's from the air. From there, the "purified" air goes through a tube, usually to somewhere near the top of the filler neck, in case you are at a gas station that has vapor-recovery systems in their nozzles (most don't these days). There are a bunch of solenoid valves that control where the flows go.

When you start driving again, the system directs fresh air through the charcoal canister, which releases the adsorbed HC into the fresh air. The resulting HC-laden air is directed into the engine's air intake, richening the mixture a bit. The carbon is now regeneraed and ready for another fillup.

When you overfill, the extra gas goes up through this system, which causes several problems: (1) the volatile components of the fuel are present in very high concentration, which will oversaturate the charcoal, (2) less volatile components which normally don't come into contact with the charcoal may bind irreversibly to the charcoal, "poisoning" it.

If the canister is toast, you are releasing HC pollutants to the atmosphere when you refill, only you don't have any way to know that. If you are lucky, the system won't throw a code. If it does, repairs may be expensive.

This question comes up all the time. I just fill to the first click, no worries.