Originally Posted by sngltrackdufus
It works pretty good forr loosening up rusty bolts & nuts & freeing up tight stuff. I use it all the time. I like it. i don't consider it in it's self as an abrasive
It is an abrasive. Get that anywhere near your valvetrain or other engine internals its almost like dumping sand in there. I know a local company around here will even void your warranty if you use wd-40 to help slip in their diesel injectors (machined to close tolerances). I think wd-40 even threatened them and tried to get them to stop telling other people that it is an abrasive. I tested it out on a camshaft on one of my engines and it can easily rub/scrape off any markings on any shims or anything it comes close to.