23-10-2020, 02:23 PM
The super cheapo oils of today have API ratings far beyond oils in common use to early 1950s and by many beyond, although the rating is not primarly based on static preservative properties. Suspicious oils were some cheap re refined grades but with the fall in oil prices most have disappeared. Keeping air flow out of the engine (including waterways) assists. If the bores are not occasionally dosed with oil rings are inclined to wedge. Ideally engine should be occassionally spun on starter to toss oil around. Mind any bungs are not digested.