Yeah it's a pretty big jump. I'm suprised that with 10.5:1 some guys still run mid-grade. I used to run 10.5:1 in the TR6C and it didn't like 89 octane. It would run but it would ping under a load. It was OK if I was just putting and not putting a demand on the engine. With 92 or better it was OK under all conditions and that was just the difference between 9:1 and 10.5:1.

I learned all I need to know about life by killing smart people and eating their brains.
Eat right ,Exercise ,Stay fit, Die Anyway!