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Gas tank capacity

The gas tank on my 2006 Honda CRV is identified in the manual as holding 14 gallons (US). When I fill it to the auto-stop of the pump nozzle, I get about 270 miles until the low fuel light comes on (indicating about 30 miles to go). I have recently discovered that if I continue to very slowly and carefully continue to fill the tank, I can add as much as another 3 1/2 gallons up to 15 1/2 gallons total added on top of the residual gas (between 1 and 2 gallons) in the tank. This gives me as much as 350 miles until the light comes on. Are there any negative issues in doing this?

You will eventually cause damage to the evaporative emission system. It could be expensive. When the nozzle trips remove it and drive on.

Rod Knox is correct.
Continuing to fill the tank after the pump clicks off for the first time has the potential for gasoline to flow into the carbon canister that is the heart of the evaporative emissions system. The carbon canister is designed to handle gas fumes, not liquid gasoline, and when it becomes contaminated with liquid gasoline you will have to replace the carbon canister–and possibly other parts in the evap system.

If you are about to drive across the Atacama Desert, you might want to add those extra 3.5 gallons, as it could potentially save your life.

On the other hand, if you live in the civilized world, you should never be very far away from a gas station when your tank runs low. While I don’t know the exact cost of replacing the carbon canister on a 2006 CR-V, I do know that this repair costs $300-400 on many Toyota models.

Overfill the tank in order to be able to gas-up less often, or preserve the condition of your evaporative emissions system?
It’s your choice.

What happens if you just don’t replace the canister?

I live in Canada & have an 06 Honda CRV, book says tank holds 58 litres or 12.76 Canadian gallons. I always stop filling the tank when pump clicks off & you really should do the same. On the highway I have made 380 miles before the light comes on.
I sure wish honda could of found room to make tank at least 2 gallons larger.
Good luck with your CRV. We love ours. Honda Bill

If you don’t replace the canister, you will probably encounter problems with filling the tank. Additionally, if you live in a state with emissions inspection, you will not pass the inspection.

VCD is correct…If the EVAP system malfunctions, the CEL comes on and you fail any emissions test…On many models, the plugged up canister will make fueling difficult…

If you stop overfilling the tank, the canister will dry out eventually and no harm will be done. Thats assuming that you stop overfilling the FIRST time you get the CEL with the code P0440.

Yes your gas tank holds 14 gallons but when you “overfill” your fuel tank you also fill up the fuel line from the tank to the nozzle as well as the entire evaporative emissions system (as Red Knox and VDCdriver have mentioned). The evap system is not meant to handle liquids and you will eventually suffer the consequences that VDCdriver mentioned. As a special bonus, if you keep overfilling the tank you will eventually get splashed with gas when the overflow shoots out of the filler opening.

You drive a Civic so 14 gallons should go about 500 miles. Is it worth all the trouble to keep overfilling the tank?

Doesn’t your manual specifically say not to do this?

Habitually overfilling your gas tank can in some vehicles, as others have said, lead to a saturated charcoal bed in the canister. If that happens, that can also lead to a dead fuel pump. As fuel is pumped out, your gas tank breaths in through that charcoal canister. If it becomes saturated, inability of the tank to breath in can cause a vacuum to develop in the gas tank’s air space as fuel is pumped out and the vacuum can cause the pump to be overtaxed and fail prematurely.

Most modern cars have a vacuum valve as a part of the EVAP to protect against this happening, but you’re better to just not “top off” the tank. With gas stations available everywhere, there’s no reason whatsoever to be topping off the tank.

“the canister will dry out eventually and no harm will be done”

I’d guess some of the heavier fractions in liquid gas are not volatile enough to escape the charcoal for a long, long time.
At least not at the temperatures the canister reaches.

Pulling a strong vacuum may drive them out, and shatter the case too.

In many parts of rural America (i.e. New Mexico) one can, indeed, travel well over 200 miles without passing a gas station. Also, I drive a CRV, not a Civic.

“In many parts of rural America (i.e. New Mexico) one can, indeed, travel well over 200 miles without passing a gas station.”

If that is the case in your neck of the woods, then clearly you have to plan ahead.
You can do this by simply refilling the tank whenever it gets down to the 1/2 mark. While this is not as convenient as waiting until the gauge falls to a lower point, all things considered–it is far cheaper in the long run than what you will have to spend for repairs by continuing to top off the tank.

…and by what you’ll spend for a tow if you are stuck out quite a ways.

You miss the point. It doesn’t matter if you establish a procedure of refilling at an intermittent level, not only are great distances extant between gas stations, but in rural America, many close at night and on weekends as well as often being out of fuel. Also, AAA offers, and I subscribe to an extended towing service.

dblacher - you asked the question and now seem to be disagreeing with the answers.

Patrick–Most of the veterans of this board are used to that phenomenon.
It happens very frequently, thus leading me to wonder why someone would ask a question if he is prepared to argue about answers that don’t conform to his preconceived notions.

The answer to your query is yes, there is a negative issue in doing this.

Have you considered putting a rack on the rear door with a spill proof gas can?