Topping off the tank when filling up

[OddDrive]

So I just did a google search and found out that topping off your fuel tank when filling up can damage your car's vapor recovery system and reduce gas mileage. Of course I find this out after topping my tank off for a big trip. What constitutes topping off the tank? My accord took over 3 gallons after the click before the fuel level reached the filler neck. I just added 2 gallons to the Ody and its nowhere near full. Does the fuel vapor recovery system really require 3 gallons of empty space in the tank to function properly?

[BigBoat]

Personal experience: I've filled the tank to the 1st click (no topping off) for the last couple of years. When is really "empty" I've been able to put up-to 20 gallons. My yesterday's receipt indicates 19.425 gallons, the gauge still had a bit of travel

If it helps, according to the OM, the low gas light comes at 3 gallons left on the tank

I believe a couple of owners have reported issues here, but in my case the many problems reported from owners of other cars like my non-Honda when topping-off really freaked me out, not worth the pain...

[0dyfamily]

We had a forum member who actually designed OEM fuel systems. His take, based on check valves and location of components on most vehicles, was that topping off was not a problem.

Right before our winter ski trip I once very carefully added almost 4 gallons to my 2003 Ody after the gas pump auto shutoff; that was years ago, with no ill effects, and I made nearly 600 miles on that tank of gas. Since then, I'll regularly add over a gallon extra after shut off whenever I refuel.

OF

[OddDrive]

We had a forum member who actually designed OEM fuel systems. His take, based on check valves and location of components on most vehicles, was that topping off was not a problem.

Right before our winter ski trip I once very carefully added almost 4 gallons to my 2003 Ody after the gas pump auto shutoff; that was years ago, with no ill effects, and I made nearly 600 miles on that tank of gas. Since then, I'll regularly add over a gallon extra after shut off whenever I refuel.

OF

That was my purpose - to get 600 miles out a tank. I've leaving on a 1200 mile trip in 2 hours. First big trip in the new Ody. Thanks for the reply.

[RiaD'H]

You can really put that much more gas in?? I've never topped off in my life probably because I read something that told me not to and I'm a scaredy cat. 2-4 MORE gallons, really? I have visions of me spraying gas all over the place......

[OddDrive]

I'm in NJ, a no self-serve state. At the local Costco, the station attendants are not allowed to top off.

[0dyfamily]

Ria, yes, I've done this. There's this one pump a few blocks away that I can pull on the trigger just enough to get a steady & continuous trickle of dispensed fuel, and as long as I can sit there and watch it tick off the hundredths of gallons, it will not automatically shut off if I do my part (i.e., don't let the fuel level rise up to where the nozzle is). Also, it's top tier fuel and ethanol-free year-round.

Bear in mind, both of our Odys are 2nd gens, but I don't figure there would be a significant difference in fuel storage & delivery system design between ours and yours.

Look at where the feed pipe fits into your gas tank under the left rear wheel well. It goes into the side of the tank, not the top. After the gas station nozzle automatically shuts off, you have an empty vapor space above that which must take up at least several gallons of volume.

As well, whenever I've max'd out the tank, I immediately started driving to start using that fuel. What you don't want is to endre a temperature change where it gets warmer on a completely full tank. That scenario can push fuel into places it is not supposed to go. I used to fly big jets, and although it is unusual to fully top off a jet's fuel tanks, if this was done during a cold winter's morning from fuel trucks that had sat out all night (as had the aircraft), the subsequent sunrise would warm up the wing, and then one might see the expanding jet fuel piss out of the wingtip vents. Hasn't happened to me, but I've known people who had this happen. Food for thought.

OddDrive, your fuel tank is larger than on a 2nd gen. I think you may make the 600-mile cub from a fully-topped-up system, but it takes really careful driving. I have a Scangauge II to help monitor TPS (throttle position sensor) angle. Speed up going down hills and use that momentum to carry you up the next hill, and all those other hypermiling tricks.

OF

[0dyfamily]

OddDrive, are you guys even allowed to bring a gas can with you for things like lawnmowers?

OF

[SFR-DSR-44]

With my previous car, a Ford Explorer, I would regularly keep adding fuel until I could see it in the filler neck. I destroyed the carbon canister as the EVAP system sucked the fuel into the canister. Now I always just stop at the 1st click.

[OddDrive]

OddDrive, are you guys even allowed to bring a gas can with you for things like lawnmowers?

OF

I live in NJ, not California. I did get me one of those CARB compliant Gas cans after Sandy. I have to say, after driving around for 9 days inhaling fumes from my old style gas cans, I can say that I can sit all day in the car with a full 5 gallon CARB Compliant can and not smell the gas at all.

[OddDrive]

Ria, yes, I've done this. There's this one pump a few blocks away that I can pull on the trigger just enough to get a steady & continuous trickle of dispensed fuel, and as long as I can sit there and watch it tick off the hundredths of gallons, it will not automatically shut off if I do my part (i.e., don't let the fuel level rise up to where the nozzle is). Also, it's top tier fuel and ethanol-free year-round.

Bear in mind, both of our Odys are 2nd gens, but I don't figure there would be a significant difference in fuel storage & delivery system design between ours and yours.

Look at where the feed pipe fits into your gas tank under the left rear wheel well. It goes into the side of the tank, not the top. After the gas station nozzle automatically shuts off, you have an empty vapor space above that which must take up at least several gallons of volume.

As well, whenever I've max'd out the tank, I immediately started driving to start using that fuel. What you don't want is to endre a temperature change where it gets warmer on a completely full tank. That scenario can push fuel into places it is not supposed to go. I used to fly big jets, and although it is unusual to fully top off a jet's fuel tanks, if this was done during a cold winter's morning from fuel trucks that had sat out all night (as had the aircraft), the subsequent sunrise would warm up the wing, and then one might see the expanding jet fuel piss out of the wingtip vents. Hasn't happened to me, but I've known people who had this happen. Food for thought.

OddDrive, your fuel tank is larger than on a 2nd gen. I think you may make the 600-mile cub from a fully-topped-up system, but it takes really careful driving. I have a Scangauge II to help monitor TPS (throttle position sensor) angle. Speed up going down hills and use that momentum to carry you up the next hill, and all those other hypermiling tricks.

OF

I didn't join the 600 mile club, but would have gotten to 520 on my last tank, had my trip not ended I'm too impatient to go less than 75 on such a long trip, and the van was full with gear and 6 people. The gas mileage achieved was extremely inconsistent, considering that my speed was very consistent. My trip home was a follows:

Filled up in Fort Lauderdale Florida at a Mobil Station.
465 miles, 19.4 gallons, 24.0 MPG

Filled up outside Savannah, Georgia, unbranded fuel station

441 miles, 19.5 gallons, 22.6 MPG

Filled up in Southern Virginia at an Exxon Station, went 394 miles at an indicated 26.7 MPG

all three segments averaged 74 - 76 MPH over mostly flat terrain. Cruise Control used most of the time.

[nomorenow]

With my previous car, a Ford Explorer, I would regularly keep adding fuel until I could see it in the filler neck. I destroyed the carbon canister as the EVAP system sucked the fuel into the canister. Now I always just stop at the 1st click.

Good to know,,,,Now I'm gonna tip to nearest .25cents of the dollar after the 1st click.
Cuz before after the 1st click, I was still able to add almost another $2+. I guess I won't be doing that now.

[RiaD'H]

I never topped off till I saw this thread............ and did top it off last time only adding 1 extra gallon. I felt like I was breaking the law.... but anyhoo, I think that's a safe amt and won't cause any problems. Not sure if this is my new habit or not.

[John U]

Some gas pumps are super sensitive and click off way too soon. Some are "looser" and will gush out.