Prius C tank capacity more than expected...

Post #15 had the answer

 

I guess what I mean is, what is the top of the filler neck? Is it the physical opening or at one of the ridges inside?

 

If fuel is no longer going in and is spilling out... then you have hit the top... it's not rocket science. Quit trying to make it more than it needs to be.

 

How about you quit being an donkey and go back to school and learn the world's population is not a copy of you.

 

Pumping lots of gas after your filler neck is full certainly does cause air pollution. How do you figure the evaporative emissions canister can hold fuel vapor when you've pumped over a gallon of liquid fuel into it?

 

Irony? Perhaps... but in case you missed it... saying I should go back to school and then making a grammar mistake...

Sorry you don't like it when people call you out on being nit-picky when you already know the answer to be less than a couple of ounces difference.

 

What you call "nit-picky", I call being specific. I was not aware of the amount of fuel that can be stored between the tank and the very top of the neck. I figured it must be substantial if you made a big deal about it. Apparently it isn't, according to you again.

I just didn't see the logic in a manufacturer including the neck as part of the overall tank capacity, nor in insulting me for being myself.

Anyway, I'll stick to not topping off the tank.

 

And that is where we came to a split. Your post made it seem like you were talking about the area outside the spout after the drain. That's why I was saying it was nit-picky. When people on this site and many others reference "topping off" they mean all the way to the top to the point they can see the gas. I wasn't trying to be an nice person, just didn't realize you weren't aware of that.

 

If you want your mpg calculation to be exact, it doesn't matter where you fill it to as long as you can visually verify the level is the same each time. The point is consistency, not a certain magical mark.

If you want to maximize the amount of fuel in the tank, fill 'er up until it's about to overflow when you put the cap on.

 

At first I didn't understand why people kept saying this. In my mind, I was thinking they implied the neck is part of the tank and that's how you get the total capacity. I see now what you guys meant was that while the neck isn't part of the tank, you can't tell if the tank is being filled or not, the same each time or not, because of the various conditions that limit this that were mentioned before, and the only way to get a consistent amount of fuel is to fill to a point where you can physically see the fuel, and keep it there each time.

I don't plan on doing this so I will no longer bother with trying to measure the capacity since it would be pointless otherwise.

 

Yeah.... it's in the owners manual to not top off the tank. Which is why I made my disclaimer earlier. I've personally never seen a case of it hurting anything, but I'm sure it can.

 

How can you pump more if the neck is FULL ??????????????
IT WILL SPILL OUT AND ONTO THE VEHICLE. It's not possible to add more into the tank after the neck is full.
Obviously you don't understand how the EVAP system works or how it's designed. You're not pumping gas into the EVAP canister. You're filling the fuel tank to it's maximum capacity, WHEN THE FILLER NECK IS FULL. The fuel remains in the tank. Vapors are stored in the EVAP canister. During the purge cycle, those VAPORS are purged and sent to the intake to be burnt though the engine.
All 1996 and newer cars have a closed EVAP system.
EVAP stands for Evaporative Emissions System. Here's a simplistic diagram of the system.

A closed system will not allow vapors to exit the CLOSED system. It's not polluting to top off the tank. Please don't spread misinformation as truth. If you don't know or don't understand how things actually work, ask someone.

 

Your fuel mileage will be inaccurate. It will be close, but not accurate. You'll find a wider range of MPG's without accurate measurement at each fill.

 

Thanks, Doctor. I didn't realize I was an idiot. Your colorful, emotional post was easy to follow, so now I know I need to go back to school and get a brain.

 

It was never accurate, and I doubt topping off will change that.

 

I'm only trying to keep information CORRECT. Obviously your emotions are overriding your ability to understand the issue's related to topping off your fuel tank for accurate MPG data.
I never said anything about continuing to fill the tank after the filler neck is filled with fuel. It's not possible and you have misunderstood the content of the information and posted misinformation. It's a simple process that allows you to get accurate MPG data and will not cause pollution. For some reason you seem unable to understand it, so I expanded on the information. Sorry if my direct approach isn't to your liking. I wasn't trying to make you out to be an IDIOT.
You're doing that all by yourself Don't take it so hard if you didn't understand. Not everyone will. Just ask questions if you're not sure. I'm trying to help, if I can. Thanks!

 

If you fill it to the top of the neck every-time, it's accurate. That's the point of doing it this way.

 

Are you saying that my car's mpg calculation will be accurate if I always fill my tank and the filler neck to the brim, instead of being off by 1 to 3 mpg?

 

Yes! How could it not be accurate. You can see the fuel level and by repeating that level and collecting the
mileage and gallons used at every fill-up. Your MPG data will be accurate.

Now the next question is: How far off is your speedometer ? Mine is right on the money, but I changed tire size.