Engine Oil Temp

[EKlem]

Some guys here at school are doing some dyno testing of air cooled diesel engines(specifically yanmar L48AE). They would like to know what type of oil temperatures they can safely hit before they start to break down the oil. The oil that the engines specifies is a 10w30 synthetic diesel oil. Does anyone know the temp that you should not exceed with this or how to find it out? The highest they have seen so far is 230F.

 

[DWeiler]

230F is nothing ,on my second genner,i cruise at 190F-195F consistantly,according to the guage/mods. DW,Ps i thought most oil start to break down in the 300F-400F range????

 

[2-ND TIME]

Engine oil temps

Do you know who makes the syn oil that is in the engine. IF so there product book ( on line ) would say what the temp is. Or this would be close to what it would take for temp?

 

[DWeiler]

Royal Purple---15w40,but i can't seem to find any tech info on it yet,nothing on there website/or bottle???? ----STILL LOOKING. DW

 

[DWeiler]

Mobil 5-40 diesel list a flash point of 235 C(455 F) if this help,i don't run this oil,it may give you a ballpark idea

 

[ENafziger]

Does anyone know the temp that you should not exceed with this or how to find it out? The highest they have seen so far is 230F. <!-- google_ad_section_end -->

We do extensive dyno testing at work. A conventional dyno oil will begin to break down around 225 - 235° F. Running a synthetic, you're probably okay to 250° or so before viscosity is to low to provide adequate shear strength, etc. Make sure you change the oil more frequently when running at sustained hotter temperatures.

Although a synthetic oil can sustain hotter temperatures before breaking down, it is not as effective at heat transfer as a conventional oil... meaning things can be getting pretty hot inside the engine.

However, as we've seen and done many times at work, you often push things a lot harder and closer to the design limits when you're just concerned with observing different trends, rather than maintaining long-term reliability.

What are you using to provide air-cooling to the engine? You may need to increase the amount of cooling to the engine to keep oil temps in check. Sometimes when running an engine at rated speed/load for extended periods of time, it's also necessary to add an external oil cooler for dyno work...

--Eric

 

[EKlem]

Thanks for the replies. They are running a mobil oil. I had suggested to one of them that they should look it up but they couldn't seem to get the info.

I hadn't really thought about the airflow to the engine but right now, there isn't anything specifically for it. It is designed for a generator application so I would have thought that it might be used in places with little airflow but maybe it is assumed that it is outside and always has some flow. We did discuss running an external oil cooler. The dyno room is probably 70F.

 

[amsoilman]

At 300 Degree F. you're pushing a petrolium product! Some metals begin to melt at this temperature if held there very long. A high quality 100 % Synthetic will withstand much higher temperatures. The Amsoil 5W-30 Heavy Duty Diesel oil for example will go to 464 Degree F. before it will flash, and it doesn't burn until 493 F. Once an oil breaks down, it will never return to its original Viscosity.

 

[EKlem]

At 300 Degree F. you're pushing a petrolium product! Some metals begin to melt at this temperature if held there very long. A high quality 100 % Synthetic will withstand much higher temperatures. The Amsoil 5W-30 Heavy Duty Diesel oil for example will go to 464 Degree F. before it will flash, and it doesn't burn until 493 F. Once an oil breaks down, it will never return to its original Viscosity.

Is the flash point what they should be worried about or does it break down before that? I was under the impression that the oil would start to shear before it hit the flash point.

 

[amsoilman]

Is the flash point what they should be worried about or does it break down before that? I was under the impression that the oil would start to shear before it hit the flash point.

There are many things that shears down engine oil, heat is only one of them. Heat will accelerate oxidation, which will cause acid developement, corrosion, sludge, and varnish, which will thicken the oil, so an oil that will sustain higher temperatures is beneficial. Combution by-products, such as soot, fuel, water, acids, and dirt can also shear the oil from its original Viscosity.

 

[JBonpua]

Yanmar L Series Engines

The Yanmar L series engines are one of the very best air cooled diesel on the market. They are often imitated by the Chinese but never duplicated. They are forced air type designed for stationary applications therefore as long as you have a room temperature air supply to the front of the engine where it takes air for forced induction to cool the engine, it will be fine. I have a total of 6 L series engines ranging from the small L40 running a trash pump to an L100 running a generator. I’ve ran my L100 powered generator for two weeks straight without shutting down with Amsoil synthetics at 100+ temps without any overheating issues.

If these engines are pushed past their designed capability on the dyno and oil overheating is an issue, ENafziger suggestion is right on and an external oil cooler might be necessary. FWIW Yanmar do make an extended run version of their L series engines that has more oil capacity and an external oil filter.