ORIGINAL: Diablo-RCU
but wouldn't you think an engine manufacturer would know their engine best?
No, not necessarily. Engine manufacurer's decide on an oil they like the best and recommend that oil and what ratio to run it at. It's easy and safe for them to do that. They do not test with all oils. Oil manufacturer's know best what ratio to run their oil at in specific applications. There is nothing magical about ZDZ's that would require some special oil. Amsoil 100:1 should be run at 100:1 or close to it, and I have run it in many, many brands of engines, including ZDZ's for many, many hours, without any issues. Amsoil does say for their 100:1 oil, that you can mix it at 80:1 for heavy-duty(or some similar verbiage) applications, such as racing....I do not think our application qualifies as heavy-duty, but I think you're safe running at 80:1 if it makes you feel more comfortable. DA recommends Amsoil 100:1 at 100:1 for their engines and it seems to work quite well.