Rotella T in all my boat motors and the couple Volvo drives that I have.

Yes, high in sink. I don't know the technical qualities of it just came highly recommended from my engine builder also. Ive always used it in my short track engine's no failures yet I twist that 9200 its a 360 w/ a spec 2 barral carb. change the oil every two races. 75 laps per night so 150 3/8 mile laps.

Zinc and phosphorus are anti wear additives. They are called reserve boundry lubricants and come into play only when you lose full fluid film protection. They help prevent metal to metal contact/wear. They also serve double duty as an anti-oxidant in your oil, preventing your oil from thicking up from oxidation.

Z&P are consumable in your engine, meaning that as you run your engine, the % of Z&P goes down. This is just one of the reasons why we change oil with some regularity. These additives as well as detergents and other additives all wear out and must be replaced.

Ken

google ZDDP and u can read for days. Zinc & Phos additives in the auto world have come way down to max 800 ppm and for the last 4 years also in the marine apps - the new oil recomended for marine Catalyst system only. It hurts the catalyst substrake over time causing failures (not to get into great lenths of tech here) is the main reason for the lower levels of these 2 anti wear additives.

I asked a Holly / Weiand tech about using synthetic oil in their blowers. They DO NOT recommend synthetic BECAUSE it makes the seals leak. What does everyone think about leaking valve seals?

On my avalanche I switched to Synthetic (If I remember correctly it was Amsoil) gear oil in my front end and had both axle seals leaking within a month. Trying to do my gears a favor and this is what I got.