Thanks Guys ...
I was thinking of the Robin/Subaru 35, 4-stroke after a good, long break-in period.
Ok then, a subject close to my heart since I just got 6 of those in this morning.
One thing for sure, these small 4 strokes hold a tiny amount of oil, 100ml.
The Robin manual has recommendations in various weights, single and multi, depending on ambient temps.
I've seen it mentioned here repeatedly that conventional wisdom holds 10W-30 to be the best all around choice.....dino for break-in then going to synthectic.
So, blasphemous as it is, let me add this. When I checked in last summer with the closest authorized Robin dealer I found it to be a mom/pop small engine repair a couple miles from me. The old timer running the place said 'that engine wants a good 30 weight'. I mentioned that here once and was chided that the old timers always say '30 weight' for everything.
Then, searching around for something else one day I found this:
Q: WHAT IS THE BEST OIL FOR 4-STROKE SUBARU ENGINES?
A: The best engine oil for your petrol-powered, 4-stroke SUBARU engine is a high-quality, mono-grade 30W oil and NOT a multi-grade. The rings on new engines will not bed properly if a multi-grade oil is used - you will just end up with a beautifully glazed bore!
Q: WHICH OIL SHOULD I USE FOR THE SUBARU EH025 & EHO35 SERIES ENGINES?
A: These engines are used on brushcutters, blowers, blower vacs and portable vibrator shafts. The owners manual suggests 10w-30 oil. Unfortunately weather temperatures above 20 degrees can cause excess oil in the air filter of these engines. We suggest (as per the service manual) that 30 grade mono be used consistently.
It's from an industrial equipment supplier:
http://www.crommelins.com.au/faqs.cfm
I, and several other members here, noted gasoline contaminating the engine oil during break-in on the Robins, surmising it washing by the piston rings. Also several guys mentioned the air filter elements becoming oil soaked.
In my case, it was mid-summer and 90+ degrees out. I went to a high quality mono grade dino oil and the problem disappeared. The Robin owners manual does mention, quote:
If multi-grade oil is employed, oil consumption tends to increase when the ambient temperature is high.
Anyway, just thouight I'd mention it here. Like all things, YMMV.