Brian interesting point on commercial fuel blends think the Davis 1/2A was made for Cox conversions originally and has favor in a lot of small ones higher ether and oil content
Model techniques in the UK has 3 blends If you look at the instruction sheets MVVS, PAW. etc they re all over the place on mix ratios if you have oil out the exhaust you have enough
lube
I just find it easier to use the Davis blends no messing with mixing
Nice thing about diesel if you go too lean it just slows down and stops a very lean run on glow hot, not enough oil and damage likely
about the only way to ruin a diesel is running overcompressed or hydro lock it martin

Think there is a low limit on oil % for long life I would not go lower than25% ( my thought)