Never top off your tank 

I have regularly topped off my tank for years. Never again. Thanks for actually explaining the problem. I generally ignore being told what to do simply "because I said so" or "because that's what the experts say", but when it's clearly and logically explained, that makes all the difference in the world. THANK YOU!!

Suggestion noted. Gas tanks are typically laying horizontally on the bottom while the engine sits higher. The gas station pump has a sensor at the tip to stop when the gas level reaches pretty much at engine height levels. If this was true, even filling the tank after the first stop would be bad. So I researched this and found countermeasures are in place: "The fuel tank typically has a vent control valve sitting on top of the fuel tank which allows only gas vapors to escape to the charcoal canister. When a fuel tank is completely filled, this vent valve gets immersed in liquid gasoline but it closes the outlet passage to the charcoal canister thereby preventing liquid gas from reaching the charcoal canister. " This is why many people have been able to do it for years ok. However, there is indeed a danger if the canister gets liquid gas: "This affects the charcoal pellet particles and it no more maintains its porous structure which then gets converted into a fine powder and would reach the purge valve and air intake manifold eventually clogging it."

Most vehicles are designed to spill out the hole instead of leaking into the vapor. But it is definitely still possible to spill over to the vapor. Great video.

I have to be honest. I started watching your video with skepticism but by the end of the video you explained it in a way that we could all understand. Thank you, I will avoid overfilling!

I do emission testing in Texas and this is the number two reasons why cars fail the test. People don't know it's bad to top off or think it's a myth. Great Vid!

Thanks a lot, Gentleman, for sincerely warning people not to overfill.

This is the first time I have ever heard of this. Why? Keep us uninformed and a shop makes off like a bandit. You are opening ears, eyes and minds. Way to go AMD! Bravo goes to you for your honesty and truthfulness!

This is probably the best and most comprehensive explanation I’ve seen on RU-vid. Thanks for making this video.

I really wish I had a general car maintenance class growing up.

Thanks a lot for that. I have to say that, I have been reading and watching a lot from engineers and mechanics about common problems. This is the first time I hear such a simple and descriptive explanation.

Wow, this is the first time I am learning about this and I have smelled these fumes before. In our country, the gas station attendants typically like to overfill maybe to get max sales. I have begun to watch your videos and I love your outstanding knowledge and talent plus integrity in your expertise. (Scott Kilmer is probably a close second!). Your videos are also so professionally done so it seems you have superb multi-dimension skills. Thank you for your videos.

I've been doing years on various brand of cars and motorcycles. I must be very lucky. Nothing happened so far. Your explanation makes sense. No more over filling. Thanks

Darn, I saw people doing it (topping or rounding up) at gas pumps and learned to do it too ever since! Thanks for the video.

Yup I just changed my purge valve out last month. The dealer wanted $600 just for the purge valve repair. I bought the part and did it myself for $60. Good thing it was easy to get to. Thanks for this valuable info.

Car care guy, thank you for explaining this. I sometimes top off my car but I won't evermore. I just didn't understand the video but I have trust in you.

Wow! You are very thoughtful and generous in sharing your knowledge. I have made the mistake of over filling my tank many times and the result was exactly as you’ve explained. I had to dish out some money to get the purge valve and canister changed out. If I hadn’t seen your video, I would have continued to overfill and perhaps reaped another round of repairs… Thank you so much for making this video! May the good Lord bless you!

You are 100% correct! I’m a retired Subaru shop foreman. I worked at the same dealership for 42 years. The last thing a tech wants to see is a CHECK ENGINE LIGHT WITH AN EVAP code. not only is it extremely expensive for the customer, it’s not a fun thing to fix. Great video.

I knew about this (and the prices!) for several years, but wondered why I had never seen a RU-vid video on it. Good work!

Great helpful visual. Every mechanic says “don’t overfill” so I’ve always listened, but it’s nice to see it shown exactly why you don’t want to overfill. Thank you!

You’re one of the only a few people who’s ever explain that in detail like that to me I will stop doing that today. Thank you.

I've been doing this for the past few years, so far my ToYo has been kind on me. I wont do it any more. Thanks CC-Nut, you are obsessed with this knowledge and to share it with all. Thank you.

WOW! I never knew this was bad for the car. I owned a 2003 Corolla for 12 years. I would fill to the cap on long trips which was almost every weekend. I was able to get an extra 2 gallons into the tank on average once the gas nozzle clicked off. On long trips, this would give me at least 60 to 70 extra miles. I use to love doing this to see how much of a trip I could get on a topped-off tank. My best was 488 miles. I maybe could have gone more but didn't want to risk running out of gas. In the 12 years, I owned the car I never had a problem with the EVAP. My current Corolla I continue to do the same things on long trips but after watching this video I will stop. I had no idea the damage I could potentially do to my car. Thanks for making this video.

Thanks for the insight, I’ve heard about not over filling your gas tank but never had this explanation. Thanks, I’m sure other mechanics are going to be very mad at you for informing car owners on what not to do. Other mechanics will lose out on overcharging for those repairs.

Thanks for that tip. I will no longer overfill my gas tank.

I have to admit this is first time I heard this explained in detail better late than never thank you good buddy for saving us a few bucks. You're a good man and hope that your business is blessed abundantly✌

In all my years, I did not know , over filling ,could cause so much damage to my car. And the reason for not over filling. Thank you for this Vital information.

Great illustration presented. Thank you so much sir for sharing it. I'm a new car owner and never thought that would be damaged to the car system brought when overfilling the gas tank. Keep it up and God bless

This all makes sense and goes against what was instilled in me many years ago. Time to stop overfilling as it is not necessary as you have explained. Thank you for this insight.

Ok, now I know now. I’ve been over filling my new 2020 Tacoma trying to get extra mile. I know now. Thank you for letting everybody know.

I think this is the clearest explanation of the nature and operation of the EVAP system I have ever seen. Thank you!

Thank you for a very informative video...never ever imagined, or heard of this before! Have noticed a lot of people topping off at gas stations - and I must admit I have done it a few times too.

Been doing it for over 40 years have never had a issue,not worth it anymore for all the right reasons,great video,thanks!

I had no idea. I will remedy my behaviour and educate my learner children. Thank you so much. God bless. You are definitely a blessing. Frederic

Thank you, very much. I have topped off my gas tanks my entire life. This being something that became an issue in 1996, explains a lot. I learned from those older than me, and it wasn't an issue for the cars of my youth. In fact, I can remember my friends and I, shaking our cars, in order to get more gas in the tank. I topped off the tank in my F-150, as recently as last week. I'm glad RU-vid suggested your video.

Very helpful! Makes excellent sense. Since in Oregon we don't pump our own gasoline, I suspect that the best way to prevent the employees from shoving extra gas in is probably to prepay for a certain number of dollars, knowing that the tank will not be quite full.

Good video, Nut. Your diagram and clear explanation really helps folks who are ignorant about how vehicles work.

I’m 60 and I’ve been brimming my tank every single time. I never knew this valuable info. Thank you so much. Greetings from Cumbria in the U.K. Stay safe and well.

EXCELLENT information. Thank you for educating people. It's a sign you are a good mechanic who cares.

As someone who loves cars and has been driving them for 30 years, I never knew the risks of topping off. I’ve been topping off for years one to get more gas into the tank and two to round off to even numbers. I won’t be doing it anymore. Thank you for this information!

I've been a DIY for years. And I never knew this. Great presentation! Great information. Thank you!

I'm glad to say that was perfectly clear and well demonstrated. I've been trying to do the same thing with many people, and I can't believe how many actual mechanics don't have a working knowledge of this!

Thanks! I always used to think this was a myth. It was very helpful to hear this from a real professional. I'm changing my ways right now. By the way, in our family it was a 1956 Chevy BelAir. I loved that car growing up.

The info CCN has been providing here is just WOW. Pure Gold

Many years ago i had a Chevy Malibu, I was one of those people who actually read the manual. It had a page explaining this, suggesting to not to top off the gas. They did not go into this much detail, but it was suggested the system in the car was designed for the owner to not top off the gas. This is an excellent explanation of how this all works.

I never realized this. Have occasionally topped off in the past, won't do it again. And btw, just had to buy a replacement evap canister (used, hope it's good- haven't installed it yet). There seem to be about a hundred elements to the emissions systems, all of which can set off the damn check engine light!!!! Update- the used canister from ebay solved the problem (I paid a pro to install it). So, after replacing the gas cap, and the filler tube, and now the canister, it's been good for 4K miles so far.

Finally someone intelligent enough to explain the why.

I've been guilty of topping off for years...no more. NOW, it's been explained. Thank you.

It was my habit over 40 years now i have to stop it thank you

Great explanation of the parts & cost! Thanks! It seems that I've been lucky - 21 years of high-filling my 1999 Australian Camry. It's a habit I'd practiced with my 1960s Hillman cars since 1972. When studying for my German drivers licence (Führerschein) test in 1999, an instruction said not to fill past the pump cut-out, but didn't explain why. I assumed it was because lots of people go on to create a messy splash-back. I never heard of an evap canister until Scotty Kilmer mentioned it this year.

AMD, you do an excellent job at giving these videos. I have watched many of them. Continue giving us many more!

Brilliant stuff! Exclusive insights to whats happening behind the scenes when you are out enjoying your day overfilling the tank.

I'm convinced! Thank you so much for your hard work and explaining in this video. I will never top it off again.

Thank you for this - have been driving for 35 years and never knew !! Much appreciated 🚙🇦🇺

On just about every car ever made made, the vent valve is normal open. It only closes to check the EVAP system for leaks when the PCM runs the test cycle. If you are getting liquid fuel into the EVAP canister it is because the roll over valve in the fuel tank has failed. In most cases, this will require a fuel tank replacement and likely a new canister. This has nothing to do with how much fuel you put into your tank. The fuel tank is designed to accept a full condition without damaging the EVAP system.

Best explanation I've heard, and I've been researching this thing for a while now. Had I heard this last year, I probably would have changed the whole system, I still might.

All gas stations should post a sign as a customer service.

Thank you for the thorough explanation. I knew about over filling potentially ruining the evap canister, but never knew exactly how..until now. Thanks friend!

Thank you so much.When I purchased my Toyoto Corolla six and a half years ago the salesman told me to never top off my tank. I don'r recall or don't think that he ever gave a reason why. I initially followed his instruction but as the years went by, I started to top off. I hope that I have been lucky and not done any damage as you described. I will follow your instruction IMMEDIATELY

As always very interesting lecture done in a very simple and understanding way. Thank you for sharing your knowledge. 👍👍👍

Absolutely amazing video! Driving all my life but never knew about this issue! So many thanks for the description and the warning 😌🙏🏼

I just found this channel and it has real good info like Scotty Kilmer. Subscribed.

Love your new logo. You're videos are very respectful and shines over all others. May God bless you and your business.

Thank you for making a video on this. I've changed so many vapor charcoal canisters on cars because people have drenched their vapor charcoal canister in fuel by over fueling.

I have a 2011 Tacoma and 2014 Rav and usually top off until I can see the gas level. Hopefully I've dodged the bullet since no "Check Engine" light has come on and I still have no gasoline smell in my garage. Thanks to you, not doing that behavior again. Dealerships should be emphasizing the consequences of this activity.

I've always thought the truest form of a Leader is a Teacher. Love your content!

Subscribed!!!! This guy is 100% right. I overfilled my car twice and both times I drove straight home only to smell gas. I got the hint to not overfill. But I didn't understand why. Now I know! Thanks!!!!!!!!

Thank you good to know i am one of those persons . Not going to do it again

Thanks for the explanation. I am one of those people trying to round up to an even number at the gas pump. Now I need to break the habit!

Love this channel. The best on RU-vid! By the way, congratulations on Mrs Car Care Nuts new whip!!!

Great video with a clear, logical explanation. I've heard this for years, but never understood why you should not do it. Now I know. I typically have let it click stop then add a little more until it click stops again. No more.

Well presented sir. If one is simply told "not to" or "must do" without explanation, then the student will learn very little, if anything at all. If you don't understand the "why", you are less likely to know the how! As a former driving instructor I always instilled the "why". It was especially satisfying when I presented this to pupils who had come to me from other tutors, for whatever reason, and they suddenly had the "light bulb" moment, usually followed with, "Ah ha! now I understand it" !!!

Thank you for this helpful information. You have no idea how much help your channel has been. Its simply the best on the internet.

No one ever explained why you don’t top off your tank. You are a good man Ahmed. God will bless you because you are honest, care, and you are not a nut like so many mechanics out there. I watch you and Scotty Kilmer all the time since I found y’all about a month ago. I’ve made lists of things I want to fix on my 2000/4 Runner. One problem is when I go to buy the items I need, men will question why I need these items, and who said I needed these items. They question why this 66 yr old grandma is speaking car so well and intimidating them. They do not care to help me find what I need, and try to sell me other junk. So frustrating!!! Thanks for educating those of us that have beautiful polished nails with a little grease under them. God bless you…Marta

Finally have a good explanation for this and THIS is exactly what my 2011 BMW is going through right now. I have the service light on. Threw a code with my mechanic. He mentioned something with the EVAP but didn't have a solid explanation, said he reset the light and sent me on the way to see if it comes up again. It did and is still one. Luckily I'm in the process of buying a 2023 TOYOTA 4runner Limited and trading my first and last BMW!! But this definitely makes sense because I am guilty of topping off my car and I do smell some slight fumes of gas. Thank you! Love you videos, Subscribed!

I see people at the gas station clicking away, trying to fill it right to the filler cap. I try to let them know it's a bad idea but no one listens.

I used to fill up to the top of the hose all the time petrol was cheap! But they were old Corollas, first was a 1979 model, the second was a 1989 one. I can’t afford to do it now 😂 By the way, this information needs to be put out there. I’ve been driving for 42 years and never knew this. Great work 👍👏

Thank you for this video. I have always done this mistake but luckily never had a problem but I won't do that anymore. Thank you again man. God bless you too.

I had no idea this was a problem, thank you for the great explanation!

Wow this was so helpful. Thank you for the illustration showing what happens. I never knew why not to, so I appreciate this!

If your house smells like gas just have a smoke and think about why

Great info. No problem in the UK. Fuel cost so much I can not afford to fill the tank never mind top it off.

Very professional advice and great educational video. Thank you

I never know this and I always used to overfill my gas tank. Thank you for enlightening me. I should have seen your vedios earlier.

Yours is one of the best automotive RU-vid channels. Very important & truthful help. God bless you. John Toronto, Canada

For years I never filled my tank I just didn't think it necessary now I know I was doing the right thing and why, thanks for sharing

Being a culprit, this information has come to me as a shock. Thank you for the advice.

Great explanation. I was telling my daughters not to top off their tanks, and your video was the perfect one to show them why. Much better than I could have ever explained it to them. Thanks!

Def helpful and informative. I used to drive long distances and would often fill right to the top. Thanks for tip.

Really helpful and comprehensive explanation. Thanks!

Thank you so much Master AMD! You are an amazing person! I am very grateful for your teaching, Sir!

Thanks for the explanation. I had a close call with this issue and saved the car by some quick thinking and remedial action once i realised what was happening to my fuel system. Don't normally fill the car beyong three quarters of a tank, but just one time I made the mistake and I was lucky. Won't overfill the car again!

I did this a good bit on my 2008 Toyota Corolla. In 2016, the “Check Engine” light came on and when I called the Toyota maintenance department, they asked if I tighten the gas cap, which wasn’t the case. Turns out there was something wrong with something in the engine. Repair cost was about $700-$800. Needless to say, I never overfilled on gas again after that. After watching this video I learned even more about the consequences of over filling on gas.

This was very good to know. I been topping off my gas tank for 30 years. Thank you.👍🏼👍🏼👍🏼

Thanks for that detailed explanation. Now I know why I smoke gasoline in my cab. You got yourself a new subscriber. Thanks again.

Dont forget to tighten your fuel cap until you hear 1 click or as long as it clicks or is tight. I used to work at a honda and ford dealership and i see alot of cel concerns, after scanning, turns out to be evap codes, then some of the mechanics would recommend a evap purge valve just to screw you. Tighten your gas cap.

This video showed up via Google algorithm, really glad it did. I was always told it's OK to round up when filling up on gas. Never knew how detrimental it is to the EVAP system. Wow, thank you for posting this video. I suspect that is why my 2003 Matrix kept triggering codes even after I replaced the CAT. Car was totaled right after I had the CAT replaced, engine light went out, but soon returned. I always rounded up when filling the tank never smelled gas, but the car was parked outside the 12 years I owned it. lesson learned.

thank you...for taking the Time and showing us "Reason" at it's best

Brilliant! Thanks for explaining WHY.

Thank you so much for doing such work!! I was doing these at the pump so many times, I might got lucky. No more of this

Thank you for informing all car drivers because I didn't know I have a friend that does this in his vehicle and he doesn't understand why this is not good but he likes to fill it and over fill it actually he did it in my car a few times without me knowing since I've watched this video I will be more vigilant from now on