I recently got my hands on a used Cobb AP3 with TCM. My car is otherwise stock, so I'm going with a Stage 1 OTS map; I am planning on upgrading over time but I'm not there yet.
Cobb offer 3 types of maps for different fuel types: 91ACN, 91 and 93. All three of them are for E10 fuels. Unfortunately, in my country I can choose either from 91 E10 or 93 E5. Cobb suggests I should go with the 91 map and use 91 E10 fuel. I'm a bit confused now because local tuners would usually suggest to go with the highest octane I can get, which would be 93 in this case.
So what difference do these 5% ethanol make? Could I still try and use the 93 map with 93 E5, and maybe log a few pulls with the AP to see if it potentially might still be safe to do so? And if so, what data should I log and what should I watch out for?