Mo-Gas!!!
I ran Mo-Gas in The Bandit for 10 years with the narrow deck 0-320A 7.4:1 comp pistons. My airboat Lycoming engine builder buddy(JR) told me that Mogas is OK through 8.5:1 (160HP) but no higher without octane booster or 100LL. I recommend buying 5 gallons of 100LL and mixing it 75/25 with mo-gas (25% 100ll) per the Canadian Govt test 10 years ago. They found the best mix of aviation/auto fuel for their Cessna 180's and Super Cubs was 75/25 to get the upper cylinder lubrication.
My Dad used the Marvel/CD3 87 octane Mo-gas mix for 30 years in his 1957 Cessna 180 with not a single issue except the smell. Mo-gas stinks. For me, 100LL is available to airboaters at a local Citgo for $3.10 a gallon, only .30 more than mid-range mo-gas. I just buy the 100LL. I do have 9.4:1 pistons now, and need higher octane.
When I ran Mogas in my RV4 I laced it with Marvel Mystery Oil and CD3 (lead additive) from the Wal-Mart Aviation dept per my Dad's technique. I never had a single issue but I always filtered the mo-gas through a chamois going into the tank. I also did long run -ups with a hot engine at 1500 prior to takeoff to get cold fuel into the carb. If you have a vapor return line, this isn't necessary. Overall, you can save alot of $$ if you fly alot and take the proper precautions.
We may all be running mo-gas someday...
Rob Ray
