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Car Talk: Rubber piece in gas tank most likely harmless

Dear Tom and Ray: I have a 5-gallon gas can that has an old-style spout, which used to have a bright-yellow cap. The cap got lost, so I got a rubber stopper to put in the end, to prevent vapors from escaping when not in use. Well, last night I put some gas in the car from this can, and not thinking, I forgot to take off the rubber stopper. You guessed it, the gas did not pour, but with a little shake, it started to flow, and a lightning bolt hit me: “Oh *#!! – the stopper fell in the gas tank!” My question is: What to do now? Will the stopper dissolve and mess up the fuel injection? How long would that take? Could the stopper roll around and block off fuel to the pump? – Bob

Tom: You can go back to sleeping at night, Bob. I doubt the stopper’s going to hurt anything.

Ray: One of two things will happen. Either that stopper will just sit at the bottom of the gas tank forever, never bothering anybody, or it will slowly disintegrate.

Tom: Some types of rubber, like neoprene, can stand up to petroleum products. Some can’t. I have no idea what the chemical makeup of your stopper is. If it was a stopper designed for a gas can, I’m sure it’ll just be an innocuous, permanent resident of your tank. Whereas if you pulled it out of a bottle of Baboon Thigh Pinot Grigio, it might break down over time. But I still doubt it’s going to cause any problems further upstream.

Ray: Even if the stopper disintegrates slowly and gradually dissolves in the gasoline, the small number of dissolved rubber molecules in any given tankful of gas probably will just combust in the engine, along with the gasoline, and never be noticed.

Tom: And if the stopper dissolves into small rubber bits (which probably is more likely), and those pieces sink to the bottom of the tank, they’ll be prevented from entering the fuel line by the “sock” filter on the bottom of the fuel pump.

Ray: And if, by chance, some very, very tiny bits get through that sock filter somehow, most cars have a second, multimicron-level filter further upstream to catch those even-smaller impurities and protect the fuel injectors.

Tom: So the car companies obviously have dealt with people like you before, Bob. And they were ready for you this time. I think you can sleep easy.


Dear Tom and Ray: My husband and I are at odds on this issue. We have a 2003 Mini Cooper with an automatic transmission. He applies the hand brake before throwing the car into park. The car then makes a noticeable creak when we get out of the car. I usually put the car in park, then apply the hand brake. If I’m on an incline, the car will roll a little, then stop – but no nasty creak. Hubbie’s logic is that it’s better to be hard on the hand brake than to be hard on the transmission. The creak just makes me uneasy! Any advice on who’s right? – Cat

Ray: Well, we’re glad this is all you’re at odds over. During my brother’s most recent marriage, they were at odds because he would put the car in park, and she would HIT HIM with the hand brake.

Tom: The good news is that neither of you is doing any damage with your respective parking methods. But we prefer Hubbie’s.

Ray: When you put the car in park on a hill, Cat, and it rolls a foot or so, that’s because the parking pawl – the device that locks up the output shaft of the transmission and prohibits the car from rolling – is not a precise instrument. It’s a ratchet with some slop in it, and it can allow the car to roll a bit in either direction before it jams into place and holds the car.

Tom: There’s nothing dangerous about that – unless you just parked six inches up the hill from Leadpipe Louie’s new Cadillac.

Ray: We’ve never seen a parking pawl break from rolling, so that’s not a concern. But if the car rolls and jams the parking pawl, it can make it hard for you to get OUT of park when you try to drive away.

Tom: Applying the parking brake BEFORE you put it in park eliminates that problem. The brake holds the car in place and doesn’t let the car roll until the parking pawl jams up. You just have to remember – when you come back – to take the transmission out of park first before releasing the parking brake.

Ray: The creak you’re hearing is just the parking brake grabbing. That’s nothing to worry about.

Tom: No. My brother creaks when he grabs now, too.