We used to have a 20 year old riding mower at our shop with a very tired B&S engine in it. Tired enough that it was difficult to start when cold, lots of oil in the air box from the breather tube. For giggles, I dumped some Restore in with an oil change and it made a marked improvement. Went for another 2-3 years before the rest of the mower rotted away or fell apart, the engine was still running decently well. It's not a "miracle in a bottle" but it can help get you along for a while.

It's probably worth mentioning that it's only capable of helping compression issues caused by scoring and marring of the cylinder walls. It will do nothing for ring tension, valve sealing, or head gasket issues.

__________________
Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]