50’s & 60’s era 2 cycle engines used SAE30 grade oil @ 16:1 ratio. This is a mixture of 8 oz. of oil to 1 gal of gas. Portions of the 8oz.of oil lubricated the rings, connecting rod needle bearings, and crankshaft bearings. The rest either became tarnish, or combusted incompletely& formed carbon deposits on the piston head and exhaust port, or was spit out as a liquid thru the muffler/exhaust or was exhausted as smoke.
To the best of my knowledge, SAE 30 was a solvent refined base stock with a low VI number & minimal additives.
Current 2 cycle mix oils operate at leaner mix ratios, burn cleaner with less deposits & provide lubrication at higher rpm levels. The most common ratio is 50:1, 2.6 oz to 1 gal, with the TCW-3 ashless oils used for the lower temp, water cooled marine applications. Lo ash oils with ISO-EGD/JASCO-FC certifications are used for the higher temp air cooled engine applications.
BTW most of the older 16:1 equipment with roller or needle bearings will operate safely at 32:1. Some of the old+ equipment/outboards had bronze bushings or journals and still requires the 16:1 mix to operate.
