It didn't make any noticeable difference on either Toyota engine I've tried- a 22RE and a 2VZ-FE on a Camry. I don't think I'd bother again- though I might keep searching for an engine it actually makes a difference in.

 

I would def. use the PCV or PVC, whatever it was called, hose if there is one. I don't know with the older trucks but with my 97 there is one. When I pulled out the hose the car started stalling. In order to keep it running i had to partially hold my thumb over the hole. I then poured half of the can in there and poured heavily when I decided to stall it. I then opened my thumb and the engine died. I got pretty nervous because I couldn't turn it on afterwards, but with a little throttle it came on. And boy!!!! there was soooooo much smoke. I was extremely embarrased becasue my neighbors came out of their house to see what was happening because I filled their whole backyard with smoke.

I waited for like 10 min and the smoke would not clear out so I took it for a spin to blow it out. Still would not stop smoking so I redlined it once and it went away. There was slight notice in acceleration and gas mileage but nothing too much.

 

I just use it in my gas tank a couple times a year & in my oil a day or two before I change it; also a couple times a year. If you remove carbon from inside the cylinder you can actually lower the compression (imo) & lose a little power. I have heard others say the carbon absorbs some of the fuel which robs power & the removal of the carbon (in effect making the cylinder larger) is offset.

It's only my opinion & I don't know of any science to back either one but I feel safer not pouring it into the engine through a vacuum line & the benefits are questionable. It is just a real strong solvent after all is said & done.


If anyone knows of any science on the removal of carbon from a cylinder & it's affect I'm all ears.