whats the reason behind using conventional oil then switching to synthetic. everything i have read states you can run synthetic from the start.

Break in. Some synthetics, due to their extremely high film strength, will not allow pistons rings to seat properly.

Learned this the hard way on my stret bike, the dran thing was smoking so bad changed the oil twice in one week back to regular oil and then rode for a month and the issue went away. Switched back to syn. oil and never seen it smoke again.

Try using the Amsoil Synthetic 15/40 marine/diesel, I have had good luck with it.

Use the Dominator series of Amsoil products. It has more additives for high performance applications. Diesel oil may actually be worse, gasoline and diesel produce different byproducts and the respective oils are designed for that purpose.

Actually the 15/40 is recomended by Amsoil if you call the tech line. "Hydrocruiser" recomends it also, it still has the additives needed. I have not used the Dominator series, I have heard that the racing oils need to be changed more often. There is a huge post on here somwhere that is about 100 pages that beats this topic to death.

Yes, true. The 15w-40 will work just fine. However, the Dominator series will actually be a bit better. Higher additive package formulated for higher horsepower engines. Also, true, that most racing oils are formulated for shorter intervals, however, this does not apply to the AMSOIL Dominator line, because it formulated with an abundance of additives to also be used for extended drain purposes and extra protection. Personally, I've run 3 seasons on the Dominator 15w-50, all of which were about 65 hours, and my oil analysis for all 3 seasons still show the oil to be good to use.

Good to know, I am in the 500HP range. I think I am fine with the 15/40, if I do any power adders I will have to look into the Dominator Oil.

+1 same with me rebuilt a Hemi and rings took forever to seat, had to go to conventional oil, then back to syn

Be careful using that Motorcycle Oil.