how are you flushing them?4T is great quality oil.
Just keep in mind that it is a different base stock (PAO base) versus the PAG based Thor and Cool Power oils.
They are NOT compatible with each other and WILL cause problems if not flushed thoroughly.
If you're going to stick with Thor or CP, go with their heavy weight oil for your engine application.
?Thanks and God bless,
Carlson Racing Engines
Carlson Motorsports on Facebook
30 years of service to the karting industry
how are you flushing them?