Thicker oil to get oil temps down?

[salgra]

Guy's I have found something odd, i wanted to share it with you.

In my profession( aviation ). I use the lycoming engine in my aircraft. A Lycoming o-360-a1a to be exact.
There is something strange in the owners manual of the engine, wich i think could be of interest to all you guy's.
here is a link to the relevant section:
http://www.lycoming.com/support/publications/service-instructions/pdfs/SI1014M.pdf
At note A it say's ; When oil inlet temperatures approach the maximum allowable during operation, it is a good indica-tion that a higher viscosity oil should be considered.
.
That, to me, does not make sense. On this forum everyone seems agreed that a thicker oil, cause a slight INCREASE in oil temperature.
What do you guy's think.

I posted it in the Car engine oil forum cause I think it would apply to all engine oil's not just aviation.

 

[Colt45ws]

It will cause a slight uptick in temperature, but its made up for by the increased viscosity. Even after compensating for the increased temp, the viscosity will still be higher than when you started. This is why you want to run as thin as the temperature and the manufacturer specifications allow. You want to avoid unnecessary heat and drag, but depending on several factors it may be necessary to go up one grade and try again.

 

[Shannow]

I don't think it's not saying that the thicker oil will get the oil temperature down, but that when temps are high, thicker helps protect the engine

 

[d00df00d]

Originally Posted By: Shannow
I don't think it's saying that the thicker oil will get the oil temperature down, but that when temps are high, thicker helps protect the engine

^^ This.

(fixed the double negative, by the way)

 

[Radman]

Higher temps lower the Cst of the oil and film thickness is lost.

If you are an aircraft technician you should have covered basic lubrication principals in A&P school.

 

[jorton]

There are "hot spots" where temps are much hotter than indicated oil temp.

 

[FowVay]

Cooling is a fine balance of capacity and discipation. Higher viscosities can absorb (and hold) more heat at a slower rate and discipate that heat also at a slower rate. It's a density issue.

Lighter oils can absorb less heat at a faster rate and discipate that heat at a faster rate.

Engine baffling plays a huge role in aircraft air-cooled engine operation. They recommend a higher viscosity simply due to the heat holding capacity of the fluid. If you're having issues with high sump temperatures then check the baffles, fins, and oil cooler for blockage.

 

[bandz7]

I have had two Z06 corvette's with an oil temperature gauge. My first Z was a stock car. I usually ran Mobil 1 5W-30. I would see operating temps b/t 210-230. My second Z06 has a supercharger from lingenfelter. They (Lingenfelter) recommend Mobil 1 10W-30 in winter and 15W-50 in summer. The previous owner only used Mobil 1 15W-50 and when that oil was in there I never saw temps above 190. Usually between 175-190.

I now have QSUD 5W-40 in there and temps are around 190-200.

This experience has always made me think thicker oil does effect the temps. Am I in the wrong here?

 

[widman]

There are a lot of things that cause temps to go up. It MAY be indicating, that in a normal engine, when temps start getting higher than normal, you may have metal to metal contact (possibly from wear) and that metal to metal contact could be causing heat. In that case, avoiding the metal to metal would reduce temps.

 

[AEHaas]

Originally Posted By: widman
There are a lot of things that cause temps to go up. It MAY be indicating, that in a normal engine, when temps start getting higher than normal, you may have metal to metal contact (possibly from wear) and that metal to metal contact could be causing heat. In that case, avoiding the metal to metal would reduce temps.


Yes. If you run a test engine at WOT the oil temperatures will decrease as you decrease the viscosity. At a certain point where the additives and oil can no longer perform optimally and metal contact begins friction increases. From this point the temperature gradually increases as you further decrease the oil viscosity.

The asparities are now in contact but oil is still flowing. With further reduction of the viscosity microscopic welds are formed and broken with the start of galling. Then a logarithmic increase in temperatures ensues, then bearing failure.

aehaas

 

[45ACP]

Originally Posted By: bandz7
I have had two Z06 corvette's with an oil temperature gauge. My first Z was a stock car. I usually ran Mobil 1 5W-30. I would see operating temps b/t 210-230. My second Z06 has a supercharger from lingenfelter. They (Lingenfelter) recommend Mobil 1 10W-30 in winter and 15W-50 in summer. The previous owner only used Mobil 1 15W-50 and when that oil was in there I never saw temps above 190. Usually between 175-190.

I now have QSUD 5W-40 in there and temps are around 190-200.

This experience has always made me think thicker oil does effect the temps. Am I in the wrong here?


I dont think you are. One of my key reservations for not running the absolute thinnest oil i can get away with is when i take ot on a one-week straight cross-country trip, and i ask myself what my oil is DOING in there. Now. As to thin vs thick oil and oil temps... A lot of the cars i like "like" 40-weight and better, and these engines tend to get their oil up to over 200 degrees, much within line with the "KV100" spec, though HTHS is more important.

A lot of thick 40s can compensate for need of a 50. Some 50s are SUPER thick, some are not so much. And ive seen SN 2W-50 conventional. Very few vehicles need that, but some people swear by 20W-50. There is a reason for this: The engines last.

i start with the engine and think of what oil will be the thinnest within recommended viscosity. If i am goin got be redlinng, burnouts, pushing it hard, i will consider that - and maybe consider one rgade thicker of oil. Case in point is the decision in AMSOIL 0W-20 (thin oil, for an engine thats super easy on oil and probably small like a CRX 1.6,) Redline 0W-20 (which i would use in ANY car needing a 5W-30 unless its rumored to not like thinner oils, like a 1990-1996 300ZX or a Subary SVX 3.3L,) and Redline 0W-30 (getting into 40-weight category here. And i think i would get it over "GC." Though, G would be a good choice on cars that like 40s.) Then i would think Royal Purple SN 0W-40 for the thickest apps. Cant see myself using the 0W-50 from Eneos. Redline 5W-50 would get that vote, and it would be summer/winter split between the Royal Purple and the Redline 5W-50, if i had an engine that needed all that.

I start on the bottom of this scale, and go up.

And if i did get a 1985 Z51 Corvette, id likely put 0W-30 in her. Redline, MAYBE GC, but likely Redline. Been eyeing up a used one. Z51 suspension package. $6000.

 

[mechtech2]

Originally Posted By: Shannow
I don't think it's not saying that the thicker oil will get the oil temperature down, but that when temps are high, thicker helps protect the engine


This is the proper explanation.