I have used RESTORE in many older cars. I bought a VW Rabbit, gas engine, with I don't know how many miles on it. There is a small hill in my town leading up past the post office. At 35 mph I would have to shift down to third to pull the hill. Plus, the engine would smoke.
I put RESTORE in and ran the engine a few hours, actually, I put a stick on the gas pedal and went to an auto auction while it ran.
When I came back, there was no smoke out the exhaust. I tried the same hill at the same speed. Instead of loosing speed and having to shift, I had to let off the gas at 45 MPH to keep from getting a ticket. It stopped using oil all together.
I've put it in dozens of vehicles. All ran better with more power, and a minimum 2 MPG increase.
I used to build racing go kart engines. The class we were in used 5 HP Briggs, all aluminum engines, no cylinder sleeve.
We ran very little oil in the engines so the oil splasher wouldn't be slowed down, advanced timing, no governor, and many times no air filter if we wanted a little intake air advantage. The engines ran on methanol.
I also ran a tight .006 clearance between the cylinder and piston. With practice laps, heat races, and main events, not counting caution laps, these engines took a beating. These were also dirt tracks we ran on, so dust ingestion was involved also.
I ran RESTORE in them, a very small amount. I could pull the head and see gray lines up and down the cylinder where it appeared scratches were. But, the cylinder was smooth as glass. The RESTORE had filled all the scores and scratches.
I also never had an engine failure, and we quit racing as winners. We beat out a guy two nights in a row that had a custom frame built, custom low resistance wheel bearings, a very expensive custom built engine, and throwing money at anything he thought would help him. He was the guy to beat. We worked hard, and beat him. I have built as many as three engines in one week to get one the way I wanted it.
We would win, get protested, and the engine torn down for inspection. Build it back the next day, and win that night again.
We had an old A-Bone cart with engines I built from used tiller blocks. I did engine and gearing, the kart owner did chassis setup, and his son drove.
That was a loooong time ago.