Overfilling Fuel Tank

[Gene K]

Is rated vehicle fuel tank capacity nominal (100% liquid volume as installed) or permissable (95% liquid volume)?

Fueling method: High until first click, wait 20 seconds, Low until first click. Is this likely to result in overfill?

Low Fuel Light Specification - 15% of rated capacity (Tolerance unkown).
Refill at Low Fuel Light - 78% (+/- 1%).

 

[JavierH19]

I stopped doing that after the mechanic told me that was the reason why my charcoal canisters pellet bag blew up and sent charcoal pellets as far as into my injector lines among everywhere else. Still not 100% sure if that's the cause but I decided it wasn't worth the effort the wait for a little extra spills worth anyway.

 

[someonesomewhere]

Low until it clicks off. Done. No rounding.

Eventually you'll kill your charcoal canister, some vehicles are more sensitive to this than others (dep on design). Getting liquid gas into the overflow is a guaranteed way to kill one.

 

[andyd]

There, 3 guys have said, Don't do it, I've learned that EVAP stuff does fine if on the 1st click. Ask yourself, do you like the smell of gas fumes?

 

[Dave Hess]

Hmmm.

I always add 1 gallon of gas but I’m on the highway and quickly burn it off at 80 miles per hour.

I need to stop overfilling tank.

 

[supton]

I wonder, if you filled up on the way home, parked, then next if it was a scorcher of a hot day, if the gas could expand and force its way into the evap system? no idea, and probably FUD.

I just don’t see the need for more than one click off. Sure, each pump might click off at different pressure point, but is it really putting that much more gas in, relative to the time spent (and potential risk of evap problems)?

On my diesel Jetta I would fill to the brim, as it was like 2.5 gallons (100miles-ish) and it sure was a repeatable fill level. no evap system, no worries.

 

[Gene K]

I wonder, if you filled up on the way home, parked, then next if it was a scorcher of a hot day, if the gas could expand and force its way into the evap system? no idea, and probably FUD.

I just don’t see the need for more than one click off. Sure, each pump might click off at different pressure point, but is it really putting that much more gas in, relative to the time spent (and potential risk of evap problems)?

On my diesel Jetta I would fill to the brim, as it was like 2.5 gallons (100miles-ish) and it sure was a repeatable fill level. no evap system, no worries.

I just hate the 10% variation when it cuts off on high vs the 2% on low. It really messes with my OCD. I was hoping the low setting would still shut off in time (I know better than to top it off).

 

[Gene K]

Low until it clicks off. Done. No rounding.

That's what I'm doing. I just run it on high until it clicks the first time so it doesn't take so long.

 

[ekpolk]

Car Care Nut (Toyota tech on YT) has an interesting video about a customer who took it one step too far. Problem for most of us is determining accurately how far is too far. Beware - it WILL be an expensive fix.

 

[TheLastWord]

Every gas pump for the last 10 years I have seen says "Don't Top Off".

Why would they say that?

 

[Falcon_LS]

Low until it clicks off. Done. No rounding.

Exactly what I do, and leave it at that.

 

[Nesterenko]

Every gas pump for the last 10 years I have seen says "Don't Top Off".

Why would they say that?

Is that really a question?

 

[Gene K]

Every gas pump for the last 10 years I have seen says "Don't Top Off".

"Topping off" is filling to 100% of nominal capacity (ie until the top of the filler neck or the overflow). I think most know that's not a good idea.

 

[Patman]

Every gas pump for the last 10 years I have seen says "Don't Top Off".

Why would they say that?

Because when people try to get every last ounce in the tank it can often cause spillage onto the ground.

 

[zigziggy]

I learned not to do this the hard way. I once had a Hyundai Accent in 2000s and I killed the charcoal canister on that poor thing (and possibly other things) but it didn't happen right after the first overfill, the thing took it like a champ over a couple of years and then one day, I was filling up and it just wouldn't take gas more than half a gallon before it clicked off, so it was taking me 10-15 minutes to fill up and was progressively getting worse over time. I think at that point the car developed all sorts of issues and replacing the charcoal canister (from junk yard) didn't fix it at all. I could not afford a new one but there was no CEL about it either. Eventually, it quit taking gas altogether more than 100-200ml at a time. Deleting the canister and leaving the ventilation open to atmosphere didn't help, so the only way to fill up was to either use a gas canister or not putting the fill up pistol in beyond an inch, which I've been doing until the car was sold. I couldn't ever figure it out.