I preferd at list 12% oil content and from my little expirience in RC cars I found that O'Donnel is the best. I don't ow someone found oil residu after O'Donnel, I found nothing but just clean engine inside after 1.5 gallons.
Altering oil content in fuel to smaller amount is attempt to gain run time and little bit performance. On winternats in Florida I didn't see any fast top notch guys were running 5 minuts straight, everybody came to refuelng, so there was no run time gain ( exsept Michael Salven-he run 6 min 15 second)
Engine needs lubricant-period! It is my opinion ( 10 years preventive maintenance manager
I stay with O'Donnel!!!!!!!!!!