Piston Temperatures of an Air Cooled Engine

Originally Posted by Shannow
No probs...I'e been trying to (re) find it for months and months



Good read so thank you mate
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Cheers
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Didn't you and I both prove some time ago, on separate continents, that a reduction in engine oil viscosity resulted in cooler head temps using riding mower engines and IR guns?

As I recall(?), I went from from a 15W50 to a 15W40, to a 10W30, to a 5W30 and noticed head temp reduction each time.
 
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Molakule,
yep, you did the heads, I did the bulk oil with a type K thermocouple down the dipstick on 5W20 through 20W60.

Given that the temperature DRIVEs heat expulsion, through radiative (T^4) and convective (T^2) mechanisms from an air cooled engine, clearly the oils were generating less heat, not carrying away more.

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Interesting, however I dont think it will sway me to go thinner in the 1980's tractors.

1 jd316 had been running thousands of hours on 20w50, now it probably has another 1000+hours on 15w40 (purchased new ?1986?)
the hour meter doesnt work now.


we have 2 more of this series tractor and they all have provided no oiling issues on 15w40..(less history with these 2 they were purchased well used)

they get worked hard.. not sure a 30wt would protect as well when they are run hard mowing fields and such.
(if it aint broke dont fix it)

In fact I snagged a case of havoline 20w50 for $1/qt that will be going in the 3000hr+ jd316.

Thanks for posting that article.. was a good read.
 
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Since most 4-cycle air cooled engines used in Outdoor Equipment specify somewhere around a 30 grade, and if i had a mowing and landscaping service, I think I would use this:


10W-30/SAE 30
 
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I tried multi weight in a air cooled and didn't like having to keep it topped off due to consumption. I went back to mono weight and no more oil burning and if it runs hotter so be it.
 
I own a Cessna 177RG with the air cooled Lycoming IO360 angle valve, 200HP engine. Using thin oil (15W-50) results in higher oil consumption and lower oil pressure. Some people claim the thinner oil may result in faster ring and cylinder wear in hot conditions. Not sure I accept that.

But oil temperature is lower by about 20 degrees.

I'd use the straight 50 viscosity oil, however, the semi-synthetic oil prevents exhaust valve sticking our operations.
 
real synthetic PAO + Ester oils listed as 30W meet 10-30 specs WITHOUT additives if you dont mind the $$$$
 
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