After all the online discussions regarding oil heat and the articles in AIM about the need for coolers I started looking at the SAE papers regarding oil and breakdown.

It appears that most current oils Dino & Syn have a "flashpoint" of over 400 degrees, this point --as I understand it , is the point when oils and their additives start to deteriorate and break down. Oil viscosity does not appear to break down until extreme temperatures are reached, higher than my bike has ever run.

If a bike is running around 280 deg what is the perceived and or actual problem?

I have a car that runs 0/30 oil, high revving and lots of underhood heat, I am not the least bit worried about the oil temp. as it is factory recommended.

Comments about water cooled are not relavent, heat is heat regardless what type of gas/diesel powered unit it is in.

Moderator----Spell Check is needed on this Forum

 

IMO, there is a lot of worry over not much of a problem. I have been riding a dino lubed Twin Cam at work for 9 years. It sees way more "heat" than the average persons bike. It hasn't melted, yet. As a matter of fact, I've yet to see a Twin Cam melted down on the side of the road or met someone who has actually damaged their bike from it getting hot.

 

My thoughts exactly.....

I know guys here in the lower midwest (where 90 to 100 degree summer temperatures are common) that run nothing but Rotella T 15W40 in their twin cams.

They think people are wasting money using synthetic fluid, even something as low cost as Mobil 1 15W50, which can be purchased for around $4.20 a quart.

These guys running conventional oil put a lot of miles on their bikes. Do they run 'warm' in the summer? I would imagine so... Have any of them had any engine problems? Not a bit....

But most oils (even conventional oils) have a flash point of at least 400 degrees. Rotella T 15W40 has a flash point around 420 degrees, Castrol GTX 20W50 is 440 degrees, etc... Some synthetics, such as RedLine 20W60, have a flash point of over 510 degrees.

But if your oil temperature reaches 400 degrees or hotter you have more problems than just the type of oil you are running.

 

This is where the oil turns to FLAMES !

 

Mineral based or "dino" oils will begin to oxidize at 250*F. At 400*F they will actually burn. The oxidation process is what causes the additives and viscosity improvers to burn off and create harmful deposits to an engine that cause sludge and other issues. While lots of people run dino oils with fine results I prefer synthetics because they don't begin to oxidize until over 300*F so your engine stays cleaner and you have a slight margin of protection over dino.

However the use of synthetics does not mean your engine is going to last longer. You won't notice the longevity issue until well over 100,000 miles. If you dino oil is changed often and you use the correct filter you should have no issues. You can get into trouble using some automotive grade oils because they don't have as much anti-wear additives as the MC rated oils do.

If you live in a hot climate and ride in urban stop & go traffic a lot then synthetics are the way to go for sure. If you have along stroke engine like a TC96 that generates a lot of heat due to the increased rotational mass of the engine internals then I would recommend synthetics as well.

 

One way to check the durability of an oil and compare different brands is to look at the oil's viscosity index number which can be found on the manufacturers data sheet usually posted on their website.

Keep in mind you can only compare the same grades like a 20w50 to another 20w50 to get an accurate indication. The higher the viscosity index number the better job the oil does staying in grade and resists shearing when hot.

You will notice the synthetic oils have a much higher viscosity index number which means their active service life is usually much longer.

Unfortunately, Harley Davidson does not publish these numbers which is why I do not use their products. FWIW the highest VI number I have found for a 20w50 oil is Brad Penn Racing 20w50 which has a VI number of 140. You can get this oil for under $5 quart

Hope this helps.