Using diesel/kerosene is quite a tried and true method that has been around forever. It works simply because it thins the oil.

Most engine flushes are nothing more than a group II base oil with some group V esters. The effect of this is not much different than diesel or kero, but you need more of it because it's basically diluted in the Group II base. Got to keep that package volume up to make it look like you're getting what you pay for.

 

I knew there would be a chemist out there somewhere, thanks

 

Kerosene and white gas (naptha) are ingriedents in many engine flush products, as seen by evaluation of their MSDS postings. How strong, how long, cranked and driven, idle only, time of operation, all these are part of the dark magic. Regardless of product - when you see the yuck that comes out you will be surprised. In some cases you could break loose large chunks of sludge that could fill the oil pickup screen. We guys like instant gratification, and sometimes a long term investment slowly applied will produce equal or better results. I have also seen Rotella work without additives. Had a Chevy small V-8, 200K+, poor service history, blue smoke at every acceleration. Removed valve covers and sludge seemed to block everything including the galley drains to the oil pan. Scooped out the "black cornflakes covered in oil", shoved something down the galleys, replaced with Rotella dino and a new oil filter, no more blue smoke after a hundred or so miles.

 

Not a chemist at all, but I do pay a lot of attention to these kinds of things.

I've gotten away from diesel/kero as I've found that a pint or quart of ATF dumped in and run at idle for a few minutes does a pretty good job as well (probably because ATF has quite a heavy detergent package in addition to thinning your oil) and I've usually got that sitting on the shelf within easy reach. For the most part, this is just for "make up" maintenance. Once it's clean it stays clean when you're using decent oil (I'm also a big fan of Rotella for flat tappet motors, as it seems a lot of people on here are as well).

I don't waste money on Seafoam or Marvel in the crank case. The both have their place, and will work just fine there, but not worth the cost. I save the seafoam for intake induction cleaning.

 

If you want a slow safe cleaning using diesel oil like rotella in shorter change intervals will help clean it out.

 

I can tell, i missed something along the road.

 

I have friends who own a salvage yard, and they will tell you the best way to kill a sludged up engine is to do a engine flush with a strong solvent.
Once you break all of that sludge loose it will clog everything, the engine will be starved of oil and it will seize.
This was a problem with some Toyota engines, they sludged up from improper oil changes and cheap oil being used.
Then someone else bought it, did a engine flush or took it to a shop for one, and it died shortly after.
They say the best thing to do for a sludged up engine that still runs well is to leave well enough alone.

 

Here's some pix - first one is a clean Disco with 180K from Street Wolf, a steady diet of Rotella and in the past Castrol, 3000 mile drain interval. The others, not even close. A couple of pix of ultra sludge in various other models. The one pix you can see the pickup screen being blocked by the gunk. Moral - use good oil frequently and let it do the cleaning job. Or tear it down to clean it, and you'll find lots of other bearing surfaces are compromised. Try to clean it all in 30 minutes, and you just might have more problems than you want. It would be really difficult to "catch up" neglected routine service with just a bottle of super solvent.

 

My engine is not running well, it's been a driveway ornament since I got it.
I am gonna take a few more swings at it.

 

This is exactly why filling an entire crank case with ATF and trying to do it all in one shot is a horribly bad idea. A bit of solvent before each oil change (depending on your risk tolerance) is reasonable (at least to me). But short duration chances with good oil will do the same thing eventually.