I bought a 1980 Olds Cutlass V8 and used Castroil GTX for 50,000 miles. I had a valve cover leak and pulled borh sides for new gaskets, what I found was shocking. There was a waxy build up on the cyl heads that I uses a small spoon to remove and had to wire and blow out the oil returns. I got some cheap 30W and used it with a quart of Marvel Mystery Oil. Ran the car 100 miles and drained oil and changed the filter, I did this several times and it slowly got cleaner. I cut open the filters and the first one was almost clogged. After that i went to M1 10-30 with no problem and it seemed to make the engine smoother and quieter. I put 120,000 miles on the car and gave to someone and they deove it another 50,000 and never an engine problem. The MM oil was a good cleaner. I'm also told that a pint of Seafoam will do the same thing.
What motor oil does the best job of cleaning?
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I've had good luck with M1 10w-30 HM.
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Which M1 did you use?
I'm going with the one changed regularly Alex for $1000 please. 
It did a great job on the engine I posted.
i´ve seen video from russian oildudes.
no matter what oil, deposits still were in place. (oil hole peek)
but after few flushes, dirt slooowly went away
conclusion was, short oci are money waste.
I don’t understand the obsession with “cleaning the engine.” The engine and combustion process is dirty in of itself. There’s soot, fuel, etc all over the place. If it isn’t causing issues, leave it be. To me, it’s like being ocd about cleaning out your sewer pipes. Plenty of doodoo to come
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Well of course it will cause issues if it builds up around the rings or in sensitive VCT components, that's the whole purpose of keeping things clean, to prevent deposits that can cause loss of performance, increase oil consumption and increase emissions.
Another vote for Mobil 1. My wife’s Corolla had Dino oil, changed by shops, until 40K when I took over. I noticed there was some brown varnish on the dipstick. After using M1 for a while, I noticed the brown varnish disappeared on the dipstick, except way up high on it. Corolla has 200k, gets M1 5w30 HM every 5k, varying brands of filters… usually upsized to Camry or Ford Ranger size (3600/FL-400s).
Yes that’s why I said leave it be UNLESS ITS CAUSING ISSUES. I see guys here with 50k on a Toyota Camry using flushes to “clean things out” on a meticulously maintained car. If there’s no oil consumption, no performance issues, etc what’s the goal here?
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The problem is that it may be hard to discern there's an issue as neglect doesn't typically result in dramatic and thus noticeable problems but rather very progressive degradation. Ring sticking can be one of those things for example, same with VCT becoming lazy because of varnish.
I'm not advocating people use flush products in vehicles that have been properly maintained. Vehicles that have been properly maintained should be clean.
What caught my eyes was your statement that "there's soot, fuel...etc all over the place" and then the comparison to a sewer pipe as if this is OK, because that doesn't really align. Oils are designed to hold these contaminants in suspension so that they don't plate out, unlike the sludge build-up in your pipes. Because these byproducts and contaminants will negatively impact the performance of the engine, formulators work to ensure that their product functions as a vehicle for these products, ensuring they end up in the drain pan, not plated out on a surface.
The water seems to hold my
in suspension quite well, thank you
OVERKILL
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Not sure how many old cast drainage pipes you've cut open, but build-up is a reality unfortunately. The fun in owning a century home.The water seems to hold my
Any euro spec 5w40
The yellow bottle Pennzoil convetional was a pretty popular one here for a few years!
Mobil 1 0w40 .. could I run that in my 2007 sequoia ?? 4.7 v8 with 230 k miles I just purchased ?
The spec is 5 W 30 and its had dino oil for many years. I was planning on mobil 1 high mileage t w 30 oyherwise.
I had the valve cover gaskets replaced. And there is some staining... icky kind of stuff. I was going to just do 3000 mile changes and see if that helps ?
The spec is 5 W 30 and its had dino oil for many years. I was planning on mobil 1 high mileage t w 30 oyherwise.
I had the valve cover gaskets replaced. And there is some staining... icky kind of stuff. I was going to just do 3000 mile changes and see if that helps ?
OVERKILL
$100 Site Donor 2021
Yep, you could definitely use it, it won't hurt that's for sure. 3,000 miles is pretty short for that oil though, you can definitely go longer than that.
The 1uz is literally one of the most bulletproof engines ever made. It’s the same engine that’s in the Taliban warlord’s land cruiser in Kandahar. Keep running whatever got it to 230k. If you run Mobil 1 for 3k in a 1uz you’re throwing away serviceable oil with tons of life left in it most likely
Back then it was just Mobil1 10w30 synthetic, there were'nt many synthetics available in the early eighties.
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Quaker State Synthetic is really the only commercial oil brand that cleans and protects the best 
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