I read a report stated it could also be used in the engine - that's why I'm wondering if anyone uses it - I've never really used additives before and read some bad things about some, especially everyone's favorite Seafoam - I did use sea foam once in bad fuel and I have to say it got me off the side of the road and home. Was filling up the old Plymouth with super and got a tank full of diesel - the driver the night before pumped the diesel into the super tank and vise versa - a lot of pissed off people that day in Shelburne...lol