How Hot Is Your Oil?

[7ShawnT]

I was on a different thread talking about my chain breaking, and Canola oil came up, and about it breaking down, because it heats up in the saw . . .

I was wondering how hot does it really get?

So . . .


It was 80 out side, and I decided to measure it!

Before going out to the woods.

After cutting for 20 min on Dead Red Pine.

But I wonder, and assume that it would get hotter , if I ran the saw longer . . .so anybody want to comment? Or take your own readings, hopefully somebody who can run their saw longer, probably a bigger saw would heat up more?

This is 100% Canola in a Stihl 021

Thanks, Shawn

 

[Dubai Vol]

Without getting too technical, the oil sump acts as a heat sink for the engine. At the same time that it is absorbing heat from the engine, it is also giving off heat to the surroundings through the walls of the tank that are exposed to air. At some temperature, a balance will be reached and the oil will be giving off as much heat as it's absorbing, and the oil temp will be steady. Twenty-five minutes is probably enough time to reach that "steady-state" condition, though more data points would be helpful. I will make an educated guess though and say that if ~130F isn't the max normal oil temp, it's close, given normal operating conditions. (It would rise if you hammered the saw harder, for example, or if it's 100F instead of 60F outside.)

The temp will differ for other saws, just based on the goemetry of the tank and so forth, not strictly on engine size, but based on how well the designers did their job of optimising the oil temp. Generally I'd say it gets enough attention that most saws will run in about the same range.

That's the thermodynamics and heat transfer end of it, anyway....

Know nothing about Canola oil, but wouldn't expect it to break down at that sort of temp: oil for frying is generally above 212F IIRC.

 

[andrethegiant70]

I would think there would be a significant difference in oil temp between metal and plastic case saws. Metal is drastically more heat-conductive. It makes me wonder if metal case saws are better for the longevity of the piston/cylinder assemblies because metal cases have good heat-sink properties. Might be a case for older saws lasting longer.

 

[Lakeside53]

The metal cases have a bigger problem with heat transfer from the muffler. Some radiant heat (on metal cased engines) is good, but enough comes from crankcase to keep the oil warm. Stihl has put in various reflector tapes etc under the muffler to protect the casing (mainly to protect the gasket), but has recently resorted to a full insulation pad in the 441.

More important than the oil tank temperature is the bar groove temperature (which the oil will immediately assume). My bars get too hot to touch under heavy cutting, but don't burn.

 

[7ShawnT]

Bar Temp?

Hmmm . . . .

I had not thought of that, I think the next time I go out and cut (this weekend is a holiday, and I won't be baking) I will try to get a bar temp.

Shawn

 

[DGG]

I thought with the "air injection" that alot of the heat was eliminated by the air blowing over the fins of the cylinder head. True or false?

Is there a synthetic bar oil that is immune from heat breakdown (like the Mobile 1 you mix)?

 

[B_Turner]

I am guessing the temp of the oil that is actually on the chains is right up there with groove temp. Especially with cutters that aren't quite sharp and therefore are getting more pressure, trememdous heat is generated from the friction. I fairly often monitor the temp of my bar and chains (just with my hands and spit sometimes), and the difference between the right chains and touch and the typical setup is great in terms of temp.

Most of us that run bio oil feel that under extreme conditions, the bio oil runs hotter than dino oil.

These reasons and more are why I suggested you run dino oil until you get a handle on things, especially with figuring out how to get sharp chains and a light touch. But you are having fun with canola so go for it.

 

[Lakeside53]

I thought with the "air injection" that alot of the heat was eliminated by the air blowing over the fins of the cylinder head. True or false?

Is there a synthetic bar oil that is immune from heat breakdown (like the Mobile 1 you mix)?

I think you are confusing two diffrent things... The heat from the cylinder is partially removed by air blowing over it from the flywheel fan.. but... don't try to touch it...

Standard dino bar oil does not break down due to groove temperature...

 

[B_Turner]

I thought with the "air injection" that alot of the heat was eliminated by the air blowing over the fins of the cylinder head. True or false?

Is there a synthetic bar oil that is immune from heat breakdown (like the Mobile 1 you mix)?

I'm with Andy that the real point of 'failure' with bar oil is typically closer to the cutting action. I can tell you that sharp square runs noticeably cooler than round due to the much higher cutting efficiency. Even more true as compared to semi-chisel. Plus of course with a sharp chain it is self feeding and with less pressure is less heat.

I am not so sure (with dino anyway) it is actual oil breakdown, just the inability at extreme condtions of heat and crud to have the chain surfaces stay clean and lubed. What happens is with the higher temps, resins, etc started baking and collecting and thus mess up the whole lube cycle. Take a look at a chain that has been overheated for any length of time and it is amazing how much stuff gets baked onto the surface.

I think an important part of a chain running cool enough is good flow of the oil from the bar to the chain and away. I bet that oil that is getting thrown is pretty hot by that time, and takes that heat and some crud with it. It is pretty amazing how absolutely clean my chain and bar stay with canola and or bio bar oil under my typical conditions of very sharp chains, green wood, and a light touch.