To top off or not to top off this is the question

[crashman]

I have been filling my tank until I can see the gas level I can usually get about 2 gallons extra in. I always wondered where the gas went so I did a quick search and found some people have had a check engine light come on. I have been doing this since new. My question is, should I stop doing this and or is there something I should check that I may have damaged?

 

[Synister]

Topping off like that is a fantastic way to damage the emissions control system, hence the CEL. There is a carbon filter back up under the spare tire that scavenges fuel vapors from the fuel tank, supposedly preventing them from escaping to the atmosphere. Topping off like that allows liquid fuel to travel down the scavenge line and can easily get inside the filter causing the charcoal to clump and no longer work. All the emissions stuff in this truck is more or less tied together so thats why you get a CEL. I would advise not doing what you are doing any more.

 

[Chad T]

I have only had my 4Runner long enough to do two fill-ups. Both times I let it go until it stops, then I let it go until it clicks again. This might be 2 seconds at most. In other words, I do a double click. Should I just stop after the single click? Want to try to keep things consistent for checking mileage.

 

[Hmebuildr]

I do it till it clicks and then round up to the next dollar

 

[mrrab]

I fill it up to the brim as well and haven't seen any CEL's. Think I too get a extra 2 gallons, i.e. 23 gallons instead of 21 gallons.

Just checked the "scavenges" in the fuel neck and there are 2. So, maybe I'll continue to fill up to the brim, but stop at those holes.

I got 121K miles on my 4Runner and have yet to see a CEL, knock on wood.

 

[jow]

I was told to stop at the 1st click to prevent overfilling. This was after I related a problem of stalling completely with instant start-ups. Only after coasting off the freeway at the next exit taken after topping off in 100 Degree + North Tx Heat. The Bell Finally Went Off! It is unreal how much gas will expand from heat and agitation. My then 1993 Explorer was flooding and stalling due to the excess gas.

Prior to this, I had a Jeep Wagoneer and Boat's tanks to cause me to stop due to due to hissing pressure releasing noises on a over 110+ degrees day. Venting the boats tank and loosening the 1980 Wagoneer gap solved the problems. The wagon had a closed system and I guess the charcoal canister was to take the pressure that was too much.

 

[mrrab]

I was told to stop at the 1st click to prevent overfilling. This was after I related a problem of stalling completely with instant start-ups. Only after coasting off the freeway at the next exit taken after topping off in 100 Degree + North Tx Heat. The Bell Finally Went Off! It is unreal how much gas will expand from heat and agitation. My then 1993 Explorer was flooding and stalling due to the excess gas.

Hmm, starting to make sense. So, don't fill to the brim in the summer.

 

[03_4x4Runner]

I have only had my 4Runner long enough to do two fill-ups. Both times I let it go until it stops, then I let it go until it clicks again. This might be 2 seconds at most. In other words, I do a double click. Should I just stop after the single click? Want to try to keep things consistent for checking mileage.

I have been doing this for 9 years with no problems at all. The reason I do it is that on several ocassions before I did it the pump would kick off and as I drove away I noticed the tank was not completely full. The pump kicked of to soon.

 

[YotaDriver]

Why not just let the pump stop when it's full and leave it at that? You need to be a grade-A simpleton to feel the need to eek ever drop into the tank.

 

[SUP3RJEFF]

I could maybe see filling completely to the top if you drive from total full to bone dry, but many drivers, myself included, fill up well before empty. Once I dip below 1/4 tank I usually fill up shortly after. That way i dont find myself clamouring for a gas station when the fuel lit goes on. Sure that extra fuel in the neck might have gotten me a few extra miles, but to what advantage? To each their own

 

[kkz]

I used to. Then was told by my mom it was bad for the environment so I stopped.

Don't Top Off Your Gas Tank! | Mid-Atlantic Air Protection

If it isn't true, big deal, losing one or two gallons per fill up is no big deal. If it is true, okay great, I'm helping the environment by not hurting it as much.

 

[4RunnerFan]

I could maybe see filling completely to the top if you drive from total full to bone dry, but many drivers, myself included, fill up well before empty. Once I dip below 1/4 tank I usually fill up shortly after. That way i dont find myself clamouring for a gas station when the fuel lit goes on. Sure that extra fuel in the neck might have gotten me a few extra miles, but to what advantage? To each their own

Not to mention that letting the gas get too low in the tank exposes the fuel pump. Gasoline above a certain level helps keep it from overheating.

 

[M1911]

Not to mention that letting the gas get too low in the tank exposes the fuel pump. Gasoline above a certain level helps keep it from overheating.

I've read that too. On the other hand, I bought my '03 new and have been running below 1/4 tank most every tank. I've got 117k miles on it, with no fuel pump problems.