wavinwayne's silly question of the day

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7,550
Location
North Alabama
Forgive the silly question, but it's something I've never really seen discussed: In layman's terms, what is the main difference between 2-cycle oil & regular engine oil? I'm not asking about the difference in the two types of engines; I just want to know what's different about the oil.
 
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550
Location
Wisconsin
I'm not a lubrication engineer, but this is my take on it: 2 stroke oil needs to be ashless so the additive package is specialized. I doesn't need VII, overbased detergents, or pour point depressants. It needs to be very soluble in fuel and long term stability in the crankcase is not an issue, so the base oil doesn't need to be a Group II or III to be effective. In fact, a Group I or ester would cling better to the internals. It must have some good friction modifiers or EP additives to cope with all of the boundary lubrication conditions.
 
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550
Location
Wisconsin
I guess nothing is completely ashless, but the less ash the better. After all, a 2 stoke burns oil on purpose. Is the synthetic 2 stroke oil an ester?
 
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3,478
Location
Millbrae, CA
Low Ash oils work better for a 2 cycle that see varying throttle speeds to blow out ash and and keep rings clean like a chain saw or motorcycle. Ashless works better for boats that have steady throttle speed. also a 2 cycle oil will have a heavy base oil "bright stock" or a "PIB" as a anti scuff additive that is partialy left behind in the cylinder to revent suffing. Synthetic esters can offer good ring cleaning and are used at a higher mix ratio like 1-100 versus a mineral 1-20 and still offer goof anti scuff wihtout the use of a smoke induceing bright stock or PIB they are the way to go. bruce
 
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