RE: DL-50 engine
You need to run the engine with the right needle settings from the beginning.
After one tank 2500rpm manufacture settings:
Run engine warm at 2500rpm for a few minutes. Close LS needle 1/16 at a time, open throttle, close throttle to idle, repeat up to the point the engine starts surging opening the throttle, then open LS 1/8 and you're right on the spot. After a few tanks run engine full throttle, adjust for max rpm up to the point where it surges after about 30-60 seconds run time, then open HS 1/8 turn or back off about 100rpm. Repeat this procedure for both the LS and HS at least once because they affect each other. Repeat again when you switch to synthetic.
I went from 3 gallons 32:1 mineral to 2 gallons Amsoil Saber 80:1, 2 gallons 90:1 and now I'm at 100:1 100+ flights.