Topping off the tank?

Usually when I fill up at the pump I just go until the handle clicks then stop. I'm usually able to put in about 16-17 gallons and drive 280 miles. Last time I filled it up waited until the click, then slowly kept stuffing gas in and was able to squeeze in an extra 3 gallons! So I put in a total of 19.5 gallons. This was right when the gas light came on, which is when I always fill up. Will doing this every fill up harm anything? I like the extra range 3 gallons offers.

 

Done this just about every time with my 1st gen and 2nd gen. Never had an issue.

 

Kewl, the only reason I ask is because I used to do it on my 2003 Silverado. The emissions system started going bad at around 200k and the mechanics we took it too blamed it on topping off the tank.

 

It may and will harm the emission Canister that holds charcoal filter and may cause problems down the road,Dont overfill, when handle stops ,you stop and remove! Too expensive to repair and diagnose and don't want to break down and be stranded because of Emmision Products and parts damages!

 

There's some kind of valve or sensor in the neck that can get damaged from topping off.

I don't remember all the info. I top off anyway.

 

This was it.

 

Yup this. I don't fill to the top where fuel is showing though. Don't recall ever adding 3 gallons more though. Maybe a gallon or so to get it to an even amount.

 

you can damage the charcoal canister. Thats how toyota "fixed" my CEL. they also replaced the gas cap...waste of money. I still add more after it shuts off bc this is the first time I have ever had the link drawn to topping off leading to the charcoal canister. I add roughly only a dollar and some change extra though, not 3 gallons worth! that may be a bit much?

 

Yeah. When I say I top off, I mean I squeeze an extra 1/2 gallon or so.
3 is probably the break stuff amount.

 

^ good advice. Where I get gas the attendant topped mine off... ended up throwing a code and cost me around $100 at the stealership to diagnosis. Continuous topping off will damage the charcoal filter... big bucks to replace!

 

This why I don't do it. Don't know if it's true or not but why take a change - emission repairs are expensive $$

 

"you can damage the charcoal canister" That's what I've heard 2

 

I just read an article (cant seem to find it)
that said to NEVER top off a gas tank.
Im sure a report has been published online somewhere.

 

This has always been a highly debated topic ( along with frequency of oil changes, Dino vs synthetic oil, which gas octane to use, What tire psi should be run, should you use ketchup or catsup, etc).

At the end of the day, there really isn't a right or wrong answer, just a wrongfully right answer or a rightfully wrong answer.

 

Useless post level: expert

 

There is a vent line that runs from the fuel tank, to the charcoal canister, to your intake. The charcoal canister is there to scrub the air of any hydrocarbons from the off gassing fumes by the fuel for emissions. If you over fill to the point that fuel enters the vent line, you will end up with liquid fuel in the charcoal canister. The charcoal cannot scrub liquid fuel, and therefore hydrocarbons escape out the other side of the canister. Sensors detect this and throw codes. If it is only a very small amount, the canister might dry out though its life will be reduced. If it is significant, or repetitive, the charcoal will become saturated and have to be replace with a new canister.

You can top off without doing so to the extent of having fuel enter the vent line, but there is no way of knowing how much, which is why it is recommended not to do so at all. I usually put a few extra squeezes in there and have never had problems. Try to put anything significant in and your charcoal canister will be toast.

 

Thanks for the in-depth answer

 

I always just let it click off, let it sit for 30 secs or so, then grab one more handle full till it clicks again. 1. to avoid too much top off, and 2. for consistency with MPG tracking

 

I always add a bit more after the click to round off the amount.(still uses cash,lol)
I had a KIA beater car a few years back and I did indeed damage the charcoal evap deal by overfilling.

 

No, actually there is only one correct answer. If you top off the tank enough to get Liquid Fuel into the evaporative emissions system it Will screw up the charcoal canister.