[m6-lt1]

No expert but the Mustang GT runs 12:1 and works on 93 fine. Not sure if this has anything to do with it but Mustangs run DI and Port injection. It’s my understanding that Chevy switching to DI on the LT1 is what let them bump compression from 11:1 on the LSX engines to 11.5:1. Based on that I wouldn’t think the Mustang having port injection as well is what lets Ford run 12:1. Again not an expert but I think Ford runs larger gaps on the coyote piston rings. No idea if that’s why they get away with .5 more compression or not.

It is my guess that anything above 12:1 is too high for 93. I have read on these forums that people see knock on their logs with 93 however I can’t remember if that’s the LT4 or the LT1 or both.

I think you’re going about it the smart way by trying to stick to 93. Some people go to high for 93 and run e85 only but then you gotta test the quality e85 you’re getting and you can no longer road trip the car as a good chunk of the country doesn’t have e85.

To confuse you even further, the current Miata runs 13:1. No idea what so ever why they can run that high.