The description for a fuel tank cap says:
You can prevent unnecessary service costs by replacing the gas cap on modern vehicles before they go bad and the check engine light appears.
Is this advertising baloney? Is there actually something that goes bad in a car if one waits until the check engine light goes off before replacing the fuel tank cap? It only takes driving on one or two full tanks until the system recalibrates. The check engine light will disappear and all will be well again. No?
I was able to find the exact verbiage on Amazon for a Toyota gas cap. It implies that you will get a CEL (check engine light) and you could, which could cost you money to get it checked out.
Here is the listing: Genuine Toyota (77300-33070) Fuel Tank Cap Assembly by Toyota Genuine OEM Toyota Gas Cap New in Original Packaging with Seal. The typical life span on gas caps is 5 - 6 years.
You can prevent unnecessary service costs by replacing the gas cap on modern vehicles before they go bad and the check engine light appears
However, I had a CEL come on, due to a tiny vacuum leak at the gas cap and I drove it for quite a while, over a year, with no ill effects. I didn't know that the solution was a new gas cap and didn't want to pay the expense of having someone locate the leak. I found out later the gas cap was the usual issue and the light went off when I replaced the gas cap. If the light comes on over something like this it isn't going to hurt anything.
Where I live in St. Louis, AutoZone, Oreillys, and Advanced Auto give you a free reading for a CEL, but I know shops were still charging for readings if you asked for one.
I've never seen replacing the fuel cap as any part of the maufacture recommend maintenance. Some vehicles now don't even have one, the seal is made internally or by the fuel hatch door.
Once on an older vehicle, I had the service engine light come on because of the fuel cap seal. I couldn't find a replacement cap or O ring to fit, so I just took the seal off and flipped it around. Fixed the issue.
