# Dumb Car Question **URL:** \ **Category:** In My Humble Opinion\ **Created:** [March 6, 2019, 3:33am UTC](https://boards.straightdope.com/t/dumb-car-question/830611 "2019-03-06T03:33:08Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![Jinx](https://avatars.discourse-cdn.com/v4/letter/j/c6cbf5/32.png) [@Jinx](https://boards.straightdope.com/u/Jinx)\ **Post date:** [March 6, 2019, 3:33am UTC](https://boards.straightdope.com/t/dumb-car-question/830611/1 "2019-03-06T03:33:08Z")
If one should need a new gas cap for your car, does one size fit all? If not, should the packaging be marked as to which cars the particular cap fits? Or, should I see the person at the auto parts counter to help me find the right one for my car? ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [March 6, 2019, 3:37am UTC](https://boards.straightdope.com/t/dumb-car-question/830611/2 "2019-03-06T03:37:05Z")
One size does not fit all. Ask the parts guy - he can look up a generic substitute. ---
**Author:** ![gotpasswords](https://avatars.discourse-cdn.com/v4/letter/g/c57346/32.png) [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)\ **Post date:** [March 6, 2019, 6:32am UTC](https://boards.straightdope.com/t/dumb-car-question/830611/3 "2019-03-06T06:32:41Z")
And by “generic” they mean it’s not made by your car’s manufacturer, but it will be an exact fit. The store probably has 100+ different caps in stock so they’ll be in back and you’ll have to ask for one rather than browsing packages on the shelf. ---
**Author:** ![Beckdawrek](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beckdawrek/32/3647_2.png) [@Beckdawrek](https://boards.straightdope.com/u/Beckdawrek)\ **Post date:** [March 6, 2019, 6:51am UTC](https://boards.straightdope.com/t/dumb-car-question/830611/4 "2019-03-06T06:51:00Z")
Yep. Ask. It can’t hurt. ---
**Author:** ![interestingtwist](https://avatars.discourse-cdn.com/v4/letter/i/c5a1d2/32.png) [@interestingtwist](https://boards.straightdope.com/u/interestingtwist)\ **Post date:** [March 6, 2019, 7:01am UTC](https://boards.straightdope.com/t/dumb-car-question/830611/5 "2019-03-06T07:01:39Z")
Also, be careful even with generic and do additional internet research. I purchased a generic cap for my car one time that set the check engine lights off. It was listed as compatible, however, I had to change to a different cap and manufacturer to get the light to go away. Something about the level of fuel fumes built up. ---
**Author:** ![Enola\_Straight](https://avatars.discourse-cdn.com/v4/letter/e/dec6dc/32.png) [@Enola\_Straight](https://boards.straightdope.com/u/Enola_Straight)\ **Post date:** [March 7, 2019, 1:25am UTC](https://boards.straightdope.com/t/dumb-car-question/830611/6 "2019-03-07T01:25:22Z")
I have recently found out that a brand new gas cap can cost up to $30. A used cap out of a junkyard is 5 bucks. ---
**Author:** ![Deanna\_D](https://avatars.discourse-cdn.com/v4/letter/d/e495f1/32.png) [@Deanna\_D](https://boards.straightdope.com/u/Deanna_D)\ **Post date:** [March 7, 2019, 1:38am UTC](https://boards.straightdope.com/t/dumb-car-question/830611/7 "2019-03-07T01:38:37Z")
> [@interestingtwist](#): > > Also, be careful even with generic and do additional internet research. I purchased a generic cap for my car one time that set the check engine lights off. It was listed as compatible, however, I had to change to a different cap and manufacturer to get the light to go away. Something about the level of fuel fumes built up. Seconding this. Apparently, my Toyota only likes Toyota gas caps. I’m taking it in for service tomorrow, and getting a gas cap is on the “to do” list. I’m looking forward to not seeing the three check engine lights anymore, and to enjoying the free Starbucks coffee and pastries at the Toyota dealer. ---
**Author:** ![Gary\_T](https://avatars.discourse-cdn.com/v4/letter/g/3ec8ea/32.png) [@Gary\_T](https://boards.straightdope.com/u/Gary_T)\ **Post date:** [March 7, 2019, 3:21am UTC](https://boards.straightdope.com/t/dumb-car-question/830611/8 "2019-03-07T03:21:43Z")
> [@Jinx](#): > > If one should need a new gas cap for your car, does one size fit all? If not, should the packaging be marked as to which cars the particular cap fits? Or, should I see the person at the auto parts counter to help me find the right one for my car? If it’s an American car from the 60’s, it may be one size fits all. For modern era cars, definitely not. And as mentioned above, while aftermarket gas caps will fit the vehicle they’re listed for, they often don’t seal precisely enough to avoid setting an emissions code and turning on the check engine light. ---
**Author:** ![Jinx](https://avatars.discourse-cdn.com/v4/letter/j/c6cbf5/32.png) [@Jinx](https://boards.straightdope.com/u/Jinx)\ **Post date:** [March 7, 2019, 9:35pm UTC](https://boards.straightdope.com/t/dumb-car-question/830611/9 "2019-03-07T21:35:05Z")
Who knew such a mundane thing could be so complicated? And, yet…you’re right about setting off that pesky “Check Engine” light! Thanks, all! ---
**Author:** ![kenobi\_65](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kenobi_65/32/13178_2.png) [@kenobi\_65](https://boards.straightdope.com/u/kenobi_65)\ **Post date:** [March 7, 2019, 10:33pm UTC](https://boards.straightdope.com/t/dumb-car-question/830611/10 "2019-03-07T22:33:16Z")
When I was in high school, in the early 1980s, the car which I usually drove was an old (1969) Jeep Wagoneer. I lost the gas cap at one point, and when i went to the local auto-parts shop to buy a replacement, the only replacement which they had available for that model was a locking variety, which cost something like $25. As that was no small chunk of change, and as i was a teenager with a low-ish Wisdom score, I creatively solved the problem with a rubber table-leg cap. It worked well enough, and we wound up getting rid of the Jeep a few months later, anyway. ---
**Author:** ![Jinx](https://avatars.discourse-cdn.com/v4/letter/j/c6cbf5/32.png) [@Jinx](https://boards.straightdope.com/u/Jinx)\ **Post date:** [March 9, 2019, 2:00am UTC](https://boards.straightdope.com/t/dumb-car-question/830611/11 "2019-03-09T02:00:33Z")
> [@kenobi\_65](#): > > When I was in high school, in the early 1980s, the car which I usually drove was an old (1969) Jeep Wagoneer. I lost the gas cap at one point, and when i went to the local auto-parts shop to buy a replacement, the only replacement which they had available for that model was a locking variety, which cost something like $25. As that was no small chunk of change, and as i was a teenager with a low-ish Wisdom score, I creatively solved the problem with a rubber table-leg cap. It worked well enough, and we wound up getting rid of the Jeep a few months later, anyway. I like your creativity! However, this car has that pesky “check engine light” on. The code says it may be a dirty O2 sensor, but before we go further, I want to check the obvious. Often, it is a leak at the gas cap with all this vapor recovery stuff going on nowadays. We’ve tightened the existing gas cap, and waited since these things are usually based on a running average. The light went out briefly, but it is back on again. We feel a new gas cap is the next step in the process of elimination. We really do not want to start replacing O2 sensors. Although one is about $100 to $150 bucks, but then there is the fear of the labor price… :eek: ---
**Author:** ![excavating\_for\_a\_mind](https://avatars.discourse-cdn.com/v4/letter/e/e8c25b/32.png) [@excavating\_for\_a\_mind](https://boards.straightdope.com/u/excavating_for_a_mind)\ **Post date:** [March 9, 2019, 2:29am UTC](https://boards.straightdope.com/t/dumb-car-question/830611/12 "2019-03-09T02:29:36Z")
Old joke: A guy walks into an autoparts store and asks the guy behind the counter: “Can I get a gas cap for a 2002 Toyota Echo?” Partsguy thinks for a minute and says “Yeah, that would be a decent trade.”