Multi-viscosity synthetic oil for older pre-synthetic-oil engines

Silviasil

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May 7, 2023
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The engine in my 31 year old Craftsman riding mower with a Tecumseh OHV-125-203015A engine calls for SAE 30 wt oil above 32° and 5w30 below 32°, then the manual reads, “Although multi-viscosity oils (5W30, 10W30,etc) improve starting in cold weather , these multi-viscosity oils will result in increased oil consumption when used above 32°.” My question is since all my more modern engines call for multi_viscosity synthetic oil for “all” (practical) temperatures can I use multi-viscosity synthetic in my old Tecumseh and NOT have increased oil consumption when used above 32°?
 

Auto Doc's

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Hello S.,

Synthetic is an improvement because it reduces both fluid friction and heat that are associated with conventional oils.

As for if it will use more oil, that is yet to be determined on a 31-year-old machine. I suspect it may actually use less oil.

On a side note: I hope you have kept the valve adjusted every few years. If not, they need to be.
 

Silviasil

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Auto Doc,
I think I’ll experiment this Fall. I mostly only have leaves to mulch this time of year and the weather is cool here in Ohio now. I’ll probably use the synthetic 10W30 and see how things go. I can always go back to the 30 wt next Spring.
You are right about adjusting the valves. They become ”sloppy” after a couple of years.
I have two of these mowers and between them I have had to replace the head gasket 3 times. A service tech told me that this engine has a design defect and it is common to have blow-by into the crankcase which blows out the bottom seal.
I should open a new thread here……..but when I decide to replace the engines what all do I have to know so that the new engines will match up with the riding mowers. The mower a Craftsman ,perhaps made by AMF, has 4 wheel steering which I really like. I can mow around a 12 in. diameter on a left turn and 24 in. on right hand turns.
Thanks for your prompt reply, Auto Doc. I drained the oil a week ago and didn’t want to add oil till I heard from other’s opinions.
 
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