Scotty Kilmers' P0420 method

[Astro14]

I'm going for it with his Lacquer thinner method. I just filled up this weekend and the code came up again yesterday (came on two weeks ago but I deleted it).

My question : if 1 gallon is ok for half tank, could I possibly use 2 gallons on a full tank? Or would this be exposing the rubber fuel lines to too much Naphtha/Toluene over the course of the tank?

For reference: It's a 200K Subaru that's ugly as sin but runs near perfect.

Thanks.

Reminds me of a member (no longer here) who loved, loved, loved, pouring stuff in his tank. Toluene, alcohol, lacquer thinner, cat-a-clean - if you could buy it, he tried it.

At one point, I’m sure his Subaru had zero actual gasoline in it.

None of it worked.

In order - Check your sensors, fix any leaks, replace the upstream one (it’s the one that matters), and if you have to, space out the downstream, finally, if none of that works, then get a cat.

 

[maraakate]

Get people to click on the video

CAN'T BELIEVE WHAT LACQUER THINNER DID TO MY CAT CONVERTER!

 

[The_Jeff]

Rev up your engines, Kilmer ALSO recommends removing the cat from the car and cleaning it with laundry detergent. That gets the gunk off the substrate so it can work again for a while.

 

[Astro14]

Rev up your engines, Kilmer ALSO recommends removing the cat from the car and cleaning it with laundry detergent. That gets the gunk off the substrate so it can work again for a while.

In general, if I can wrestle a rusty old inoperative part off the car, it gets replaced with a new part.

 

[PandaBear]

Yeah Scotty told us once to use laundry detergent to clean the cat too. He should be banned from YouTube for this. I don't think home remedy can remove the phosphorous poisoning the platinum on the cat, and laundry detergent likely will add even more to it.

If you just want carbon cleaning you can soak it in a bucket of solvent.

 

[E150GT]

Dont waste your time. I have tried fuel system cleaners. Catalclean, New sensors. Warmup only for 30 seconds before driving off. No excessive idling. A border line cat is just as good as a bad cat except the code may go on and off and on and off but it will never go away. All it takes is one time for the cat to see a condition it does not like and throw the code and starts the cycle all over again. If youre already getting a code its probably too late.

 

[kebabaluba]

How about good old water decarbonizing trick?

 

[Chris142]

This is not a gas cap issue?

Not if it's a P0420

 

[Nukeman7]

First off, let me say that I despise Scotty Kilmer and his clickbait YouTube channel designed to only enrichen his banking accounts. I would not spend 5 seconds listening to his ridiculous overblown ranting spiel on anything technical.

With that said, he might not be totally wrong on his claim of temporarily restoring catalytic converter performance by adding lacquer thinner to the gas tank. I base this upon the positive results I have had with using Cataclean to eliminate P0420 codes on two different vehicles. Cataclean is primarily composed of Acetone along with some Isopropanol and Xylene supplements. Lacquer thinner is mostly Acetone with minor amounts of other aromatic solvents.

 

[martinq]

I just remembered we were getting P0420 in the 2010 Nissan Cube in the last year. I've reset the code a few times but I don't think it's come back since I added fuel system cleaner and started using Valvoline Restore and Protect 5w30 about 5 months ago.

I'll need to re-scan the ECU to verify it's not there but I was driving it yesterday and I'm sure I would have noticed a CEL.

Just checked my notes and we had P0420 in Jan 4 and 23 of 2026. Don't think it's come back since.

 

[Chris142]

Yeah Scotty told us once to use laundry detergent to clean the cat too. He should be banned from YouTube for this. I don't think home remedy can remove the phosphorous poisoning the platinum on the cat, and laundry detergent likely will add even more to it.

If you just want carbon cleaning you can soak it in a bucket of solvent.

He also recommended compression fittings on brake lines

 

[maraakate]

He also recommended compression fittings on brake lines

Wouldn't be surprised if he advocated using compressed air to remove a brake caliper piston. There's special tools to remove them and not to mention such a thing is very dangerous.

 

[BC1]

Wouldn't be surprised if he advocated using compressed air to remove a brake caliper piston. There's special tools to remove them and not to mention such a thing is very dangerous.

The special tool is the air compressor. Small piece of wood between the piston and caliper body to stop it. I have done it several times. No more dangerous than most things car related.

 

[Paco Pena]

Helps to make sure the car is good and hot before testing.

Paco

 

[maraakate]

The special tool is the air compressor. Small piece of wood between the piston and caliper body to stop it. I have done it several times. No more dangerous than most things car related.

No. Most people just put air through it and it pops out like a bullet and can hurt people. Wood, rags, etc. is best, but there are dedicated pliers that grab the inside of the piston and you twist to pull it out.

 

[PandaBear]

No. Most people just put air through it and it pops out like a bullet and can hurt people. Wood, rags, etc. is best, but there are dedicated pliers that grab the inside of the piston and you twist to pull it out.

I just use a C clamp and sometimes also a piece of wood (you don't need the wood really). C clamp is probably $3 at Harbor Freight.

Where in the world would a normal human get a compressor at home? For what?

 

[4wd]

Yes, it's been a few years. Wanted to be close to his daughter? But by definition, still a Texas native. That is, unless Texas has their own definition of native. I do know true Texans are pretty sensitive about that stuff.

https://en.wikipedia.org/wiki/Scotty_Kilmer

 

[BHopkins]

https://en.wikipedia.org/wiki/Scotty_Kilmer

Thanks for correcting me.

 

[4wd]

Thanks for correcting me.

He’s a hybrid !

 

[JoeDirt41]

I’ve had very good luck with Cataclean. I’d try that first.