I went through a car wash with my gas tank cap off...what to do?!

so, how much trouble am i in??? i didn’t notice until i got home and my husband came out to help get our sleeping 3 year old into the house. he saw it first and was not happy. he was even less happy when i told him that i couldn’t believe that i had done that, especially since i had just driven through the automatic car was, too! what to do??? we haven’t driven the car anywhere yet.

Did you get a wash at the gas station directly after filling with gasoline? If so, was the gas partly ethanol? If so, the ethanol will absorb what little water MAY have gone into the filler. If not, buy some ethanol and put it in the filler to absorb the water. The product is called HEAT. It comes in small plastic bottles. I’d get a couple. You can get it at Autozone or Wal*Mart. If you go to Autozone, they’ll have your new gas cap too.

mg mcanick,
thanks for replying so quickly!!
i don’t remember seeing a notice saying that the gas was partly ethanol (usually i do notice that). i did go through the car wash right after i filled up. and unbelieveably, i do still have the gas cap! when i got home, the flap was partially closed and the cap was wedged between it and the car. hopefully, that means that not too much water got in?!

The car wash’s mechanism probably closed the flap. It’s not a service they generally offer, but it probably kept some water out of the tank. I’d still get some HEAT into the tank before driving any more.

How do folks keep doing this? I’ll betcha this is a dozen times I’ve read the same question this year. Don’t you (anyone) usually remove the gas nozzle, put it back on the gas pump, then put the cap back on? Guess I’ll go and complain about folks not flushing public urinals now. Rocketman

well, i have never, ever, ever done this before. up until this point, i have always done exactly what you just said, adding in the extra step at the end of grabbing my receipt (when a receipt actually does come out, that is) before getting back into my car and going on my merry way. this time, however, i was consoling my very sleepy 3 year old (who was in her carseat in the backseat) while letting the gas pump do its thing. believe me, i can’t believe that i did this either.
and for the record, i don’t like it one bit when folks don’t flush the potty, public or not.
in all of the times that you have read about this problem, do you remember what some of the fixes were? if you do, would you be so kind as to share?
thanks a bunch.

That little metal flap the nozzle pushes out of the way should have stopped most of the water/soap getting into the tank itself. I think the thing that got hurt the worst was your ego in this situation.
As another poster mentioned grab a bottle of HEAT, or other “dry gas” concoction, and pour into the tank for good measure.

thanks for the advice! my husband is on the way to pick up some HEAT or whatever else the guy at the automotive shop suggests. i’m sure they get that question there a lot, too. and yea, i do feel like a nincompoop for forgetting to close the cap. in all of my 23 years of driving, i have never, ever forgotten to replace the cap and close the flap. oh well, at least i don’t think that i will ever forget to do it again! :slight_smile:

You did no damage. If it troubles you at all, do as the others suggested and put some type of gas drier in the tank. Don’t believe me? OK . . . try this . . . cut a hole the size of a quarter in a piece of cardboard and stand about 4 feet away from it, and then use a garden hose to spray back and forth. See how much got in? Even if you tried to get water in . . like those water pistol games at a carnival, you probably wouldn’t get enough in to make a difference. Could it possibly hurt? Yes. Did it? I really doubt that you got hardly any water in the tank. Rocketman

Rubbing alcohol is probably cheaper and you likely have it at home already. Just pour it in and it will mix with the water, too.

Rubbing alcohol may have the same alcohol in it, but it will already have more water in it than you want. Heet will have some water in it but far less. The difference is what the Heet can pull out of the tank.

I don’t know from actual experience, but I think that if the water were going to cause trouble, it would already have done so and you’d be stuck within a few hundred yards of the car wash an engine that won’t start. Water is heavier than gasoline, so it would sink to the bottom of the tank. And the fuel pump pumps … from the bottom of the tank.

My understanding is that a small amount of water in the gas tank from condensation is more or less normal. Gasoline and water are very slightly miscible and that’s enough to keep the water in the tank from building up over time. It will presumably eventually get rid of any water that actually made it into the tank.

If it were me, I’d probably add a bottle of Dry Gas (anydrous isopropyl alcohol) or something similar to the next two tanks, but you probably don’t really need to.

Here’s a link http://yarchive.net/chem/gasoline_dewater.html

I did the same (silly) thing! I was wondering if you tried using HEAT and whether it worked?

9 year old post… the original poster and/or the car is long gone.

1 Like

OP is gone, but same problem has come up. If you think your short term memory is faulty, wait until you are my age; 73. Follow the 9 year old advise add some Heet or other “gas drier”. You will be fine.


And, despite one or two people having recommended a bottle of Isopropyl Alcohol, do NOT do that.
Most Isopropyl Alcohol is labeled “70% alcohol”, and the remaining 30% is water.
Why would people think it was appropriate to add MORE water to the gas tank?