'88 XJ, Renix 4.0L (cat-less, CAI, 2.5" cat-back), ~ 175K miles.
We have E85 (85% ethanol/15% gasoline) on the pumps were I live (Oslo, Norway) at a very affordable price.
I figured I could try to run 50/50 E85 and low-grade gasoline. 93 and 95 octane are my choices, this it would equate to...