My Jeep has had a misfire in cylinder 1 and 2 since June, with the check engine light staying on and rendering it unable to pass state inspection. The misfire was due to low compression in those two cylinders, and likely from worn cylinder walls and/or rings/seals, as verified by wet compression test (not a valve issue). I put a bottle of Engine Restore in my oil late last summer, and started to see the CEL disappear occasionally, but not long enough to pass inspection. Thankfully, because of the pandemic, the rules were relaxed and I had some time to save up for an engine rebuild.
Well, two weeks ago, my CEL turned off, I cleared the stored codes, and it hasn't turned back on. This morning, I took it to the local Firestone and it passed inspection!! I saw an immediate compression increase with Engine Restore (as verified by my compression gauge), but the full effects took about six months to materialize (I'm not driving much). A $12 bottle of goop saved me a $6,000 engine rebuild. I almost gave the inspection tech a hug in the parking lot, I was so happy.
If you've got an older engine that has lost some compression over time, it's definitely worth a shot to use Engine Restore. However, if you've got a newer engine or a more complicated one, DO NOT use it. VVT, turbocharged/direct injection, etc requires extremely light oil weights to pass through tiny ports, and this will plug them up and kill your engine. My engine is a 1999 4.0, single cam, pushrod I6 that was originally based on a tractor engine from the 60's, and takes 10w-30 oil.
Today is an awesome day. It's like getting another stimulus check, except we saved for it and it's already sitting in the bank in cash just waiting to be invested.