Snake Oil additives ,some do work.It does come with a price
 

In all purposes these additives are mechanical bandaides ,these generally are only their to help your current issue short term ,not a cure in most cases .This was mine and I was knowingly going into it with that thought in mind, it proved it was short term in this case .Rather than take a cans word for it I was skeptical like all of you out their when it comes to miracle additives ,this one was a case a few yrs ago and I decided to do a little test.The motors health was not good at all ,an 1983 617 turbo motor 300cd I had purchased with a no start issue ,2 cylinders were reading poorly around 180 that I found out after doing a thourough check list on all assoc. no start problems ,BOUGHT ENOUGH OIL FOR 2 OIL Changes and 2 cans of risolone engine compression restore .First oil change with filter was to get any washed out oil with diesel out of the crankcase. No start , next was to pull ,refill with the risolone product added to the oil and it worked .To endorse is not my intention but to inform ,my guess these products sell to what some may decide is a good deal less than a rebuilt motor ,the problem is the car maybe resold to an individual unknowing it could be a lemon ith these helper additives so be aware and thats my interntion to inform and not sit as an advocate.In other cases it will clean internal issues as in some cases with trannies,this could be long term but again its usually a trans that was not taken care of that is being assisted. .If you were to gather and study each can its mind knumbing but to realize as cars and motors get older its likley someone has relied on these products and its best to keep it in mind .Does it work ,the answer is yes and no ,in some cases, but at a cost and only short term.
The motor was pulled after giving up a yr later and I replaced it with a healthy one .

Generally I am skeptical of ' snake oils ' for engine problems...But where the problem is the same as can happen in automatic transmissions... the build up of varnish .... where parts are a tight fit... and the method of snake oil operation is being a varnish dissolver I have had it work...
Specifically Hydraulic Valves... sticking.... I had Rislone cure a sticking hydraulic tappet ...
I applaud your attitude about changing out the whole system after the product is used ...
Then engine I used it on was in good shape .. except for that stuck tappet ... and I drove it for many years after that.. but used better oil than the previous owner had used....
Old timers may know that many engines are designed so that a hydraulic tappet can be extracted from the top.. just by undoing the valve train above it.... and the engine I had that would work on all except the front one... the hole in the head would not allow R and R without pulling the head... So I tried ' snake oil ' and that time it was really helpful.

Did you do any other diagnostics or repairs, or just dump a can of snake oil in and drive it until it blew up for good?

I've never put any of the magic additives in any of my Mercedes' but I did put the product Sea Foam in an Isuzu Trooper that had a ticking lifter noise. Followed the instructions, which was add the stuff, drive at least 40min or miles and then change the oil. Ticking lifter noise went away and didn't come back for the remainder of my ownership.

Good Question ,Its a 2 part answer ,given the abundance back then of available 617 motors here in Houston I knew it was an easier task to grab up a donor car and prove its engine health vs head work or going into the block ,I chose to do this test since at the time I was swimming in these cars.It was mentioned at time of sale I would have to replace the motor ,being it was a 300cd I was ok with that ,and the resulting end was to pull the motor for a donor replacement in the very beginning .Alot of friends who are mechanics would always ask if it was still running ,some even gave it a name ,ticking time bomb.The rings had slap in them ,an up and down play that comes with wear and the heavier risolon product took up the play ,the band aide in a can remark.I would have liked to have performed a better diy project that gets more attention but sometimes its really about plug and play and saving a few dollars.

I remember one purchased 190d automatic that I posted here about was a trans x benefactor,again some yrs back .I bought it because it was so clean ,the trans issue was no 3rd or 4th until it was fully warmed up.I remember driving the car on the feeders until it decided it was ready to move up the gears.I thought I could just keep changing the fluid and filter at a more frequent timeline of every 5 months to bring it back and that got old quick .The 4th trannie service I put the trans x and was surprised one early morning after the weekend it was back with all its gears.Its borrowed time with used cars, the warranty is you with a wrench in hand ,parts on the bench and a repair book with a pot of hot coffee just started..

Trans-x isn't available near me, however I have had excellent luck with "gunk transmission medic" which I believe to be a similar product. I had a bad flair from 1st to 2nd on my w126. Fresh fluid and a bottle of that and within a week it was gone. This was in a car that had been sitting for two years prior to my ownership and had probably built up some varnish.

You just have to have realistic expectations for these products. They won't fix mechanical problems, but things like stuck lifters and transmission check balls are well within their wheelhouse to fix.