Ok....back from an ultralight site.
this is a pretty great article for noob info about oil & air-cooled 2-strokes.
Choosing Oil
Doesn't mention jack about synthetic though. The site sells synth, semi-synth, & dinosaur juice.
Here's what I'm picking up (correct me where I'm wrong):
detergent is good because it keeps rings from sticking.
lower viscosity is good because it reduces gunk buildup.
too little oil can scrape up your insides. (sounds like a cause of engine lockup)
too much oil can cause smoke & spark plug problems (sounds like it causes sluggishness)
how many did i get right?
anybody ever try this Lucas semi-synth?
[Lucas Link] how did it work out?
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In my personal opinion...
Detergents are kinda gimmicky, I suspect it's mostly a promotional tool. A well tuned two stroke & the proper mix shouldn't have ring sticking issues - if it does, it's either too heavy an oil mix or a very high mileage engine. If it's the latter and there's some heavy buildup - a top end rebuild is prolly in order in any case - but there's also a product called
"Ring Free" that works quite well... tho I don't bother w/it for these things heh
Viscosity is somewhat irrelevant w/a premix, tho the stuff used for leaner oil/fuel ratios tends to be thicker, before it's mixed ofc.
Too little oil is one of the causes of seizure, yep - but too much oil can be just as bad w/heavy carbon & unspent oil buildup, sticky rings & hotspots in the combustion chamber.
While not the most flattering of pics, a lil while ago I developed a pretty massive head gasket leak on my beater bike, one I've pounded on for years & has about 8-9000 miles on it now.
So... for the first time since I built the silly thing, I hadta pull the head off to fix it - and after all that mileage, this is what it looked like;
The pics don't do it justice however, there's what looks to be scoring on the cylinder wall but it's so slight that it can't be felt at all & I suspect it's frm running the stock air "notfilter". The buildup of carbon on the piston is a slightly greasy layer so thin you can still easily see the etched "5" on it and while there's more on the inside of the head, it's still minor for such a "high mileage" two smoker & easily cleaned w/a shot of carb cleaner...
Which I didn't even bother with, jus' wiped off the head gasket & bolted it back down w/new fasteners (lock washers were so rusted they weren't heh).
So - as that's a 100:1 engine (save the first 500 miles or so, that was 50:1 - all I could find at the time) you can see that even w/such a thin oil/fuel mix you can get some buildup *shrug* it was Amsoil 'Injector' for the 50:1 & Amsoil 'Saber' for the 100:1 BTW & yes, that bike still gets beaten on regularly & yea, it still smokes the local peds lol