Way back in Feb 2020, i ran a comp test on my 4runner. I tested the engine hot, throttle body not held open. The mileage at the time was about 191k and I know the previous owner had done a headgasket on it and I assume, a valve job.
The results were:
#1, 149
#2, 130
#3, 140
#4, 110
The vacuum gauge shows weak rings and I think mostly that is #4.

In May 2021 I did another hot test, again throttle body closed. The mileage was approx 195k.
#1, 150
#2, 140
#3, 147
#4, 115

Now the mileage is 200k.

I had been running Engine Restorer for a few thousand miles.
Latest test, hot, throttle body held open:
#1, 155
#2, 145
#3, 145
#4, 109

I tested and observed that holding the throttle body open(#1 cyl test) accounted for an increase of 4-5psi.

conclusion: Though I had seen videos of others testing Engine Restorer on YouTube with positive results on lawn mower engines, and that is what convinced me to try it, I cannot prove it did anything for my engine. Perhaps the results are conditional, like it helped minor cylinder scoring on #2 but did not help the rings on #4.

Either way, after recent timing adjustment, oil change, idle adjustment and spark plugs cleaning, the damn thing still runs too good to take it apart!

If you’ve had better results with Engine Restorer, let us know.

 

About all any of these snake oil products might do is free stuck rings.

And hydraulic lifters, if an engine is equipped with them.

 

#4 is a bit concerning.

I think Restore is an oil thickener. Thicker oil can reduce blow-by, but increases resistance. It won’t clean old oil sludge, though. I’ve seen Rislone work pretty well at freeing up stuck rings. Worth a shot. If you try Rislone, and see some improvement, sometimes a second application helps. I’ve never seen a third round help.

But as a rule , I’ve never been fond of most additives.

 

good input, i’m not fond of additives either. I don’t think they are stuck, but someday I’ll get to the bottom of why the low comp on #4.
when i was a kid in the late 70’s, my dad sold Slick50 oil treatment. There was a Briggs & Stratton engine display that had a plexiglass sidecover and ran without oil. Being an honest guy and wanting to stand behind the product, my Dad tried the engine flush product and Slick 50 treatment in his own Corvette. The results, due to the engine flush we believe, were not good and the engine required a rebuild. It was evident to the machinist where the treatment had coated internal engine parts.
I hadn't touched an oil treatment since then before trying the Engine Restorer.

 

I’d consider a oil thickener a treatment. Much like Alumseal, Barr’s Leak, or any of those headgasket-sealer-in-a-can. They mask the underlying problem(usually just long enough to get the vehicle sold).

A oil cleaner has some merit. It’s actually trying to correct a condition. Besides Rislone, I’ve also tried BG 44k Moa. Rislone is quite a bit cheaper. I’m sure there are many, many others.
I’d recommend doing a fresh oil change, and replacing some of the new oil with a cleaner. It’ll turn coal black very fast, but I’d run it for a few hundred miles, then change out the oil and filter. The cleaner works best on longer drives, as opposed to short hops.
Ifyou see zero improvement in the compression then further cleaner is probably pointless. But if you see #4 start to move up a second round could offer more gains. Make sure to monitor oil level while the cleaner is in the engine. It can cause oil consumption from thinning the oil.

You can also pull the plugs and put some ATF into each cylinder and let it sit for a few days. ATF is a very effective cleaner on carbon and oil sludge. Make sure to do a oil change soon after. The real old school guys would drain the oil, fill the crankcase with ATF and then run for a few minutes. But that’s too dicey for me. Fine line between cleaning and destroying.

 

GM Top Engine Cleaner soak in the spark plug holes has been used for years to free stuck rings.

Personally, I would try Rislone first because it's going to be cheaper.