I would run Amsoil 4t as a break in oil. Works great with gas and alky.And stick with it from now on.My sidecover temps dropped 13 degrees with the Amsoil 4t.
Lucas medium or jr.drag kart oil is also a great choice."High Zinc" content which is good for break in and for long term use.
If you want you can also use the Thor oil with Lucas #10063-1 zinc plus engine break in additive.You add 1 ounce then top off the rest of the way with Thor oil then let it break in.Drain/Refill.
^ NO NO NO NO and H - E - Double hockey sticks NO!!!!!
If you use 4T, followed by Thor, I can guarantee you that you will blow that engine up!
Two different base stocks that WILL NOT mix! PAO & PAG oils repel one another and WILL cause problems!
Simply use the oil that you are going to race with.
There's nothing wrong with using high zinc or zddp additive break=in specific oils, just be CERTAIN that they are compatible with your race oil.
We used to (for 25+ years or so) break in everything on Cool Power Gold (caster blend oil,) but have since gone to just breaking our engines in on the same oil that we race with. No issues whatsoever.
I was thinking this was a new/fresh rebuild and no other oil had been put in it since rebuild.
In that case my opinion I would choose either Amsoil 4t or Lucas Kart Oil as the only oil I would use in it period break in and long term use.
""I see that I didn't read that he was in the end he was going to Thor oil after break in or he had already put Thor oil in it and ran it some.
If the engine had Thor oil in it at all and then you refilled with Amsoil 4t it would be doa
"Brian is absolutely correct it would be the end of your motor."