Motorcycle Oils vs. Automotive Oils Revisited 2010

The debate of oils has resumed. We here at the CB750 Preservation Society are presenting this article for educational purposes. We portend no claims of expertise in this area, but rely on the extensive research and expertise of others. Keeping that in mind, here is a brief synopsis of what we found and what it means to you.

As far as I can determine, motorcycle specific oils have been being manufactured for racing since at least the late 1940's by companies such as Castrol and Torco. As to when these oils started becoming commercially available to the public is unclear. What has become clear, however, is that many of todays (2010) automotive oils have changed in their formulations, making them incompatable with the requirements of most motorcycles. This has happened primarily for two reasons. One is technology improvements in both engine manufacturing and oil refining. The second, and perhaps most responsible, is environmental standards, which is forcing the oil manufacturers to eliminate certain additives that have been deemed toxic to our environment. In reformulating these oils, certain new additives, called "friction modifiers", are being used which work well in engine only environments, but not where engines and transmission share the same oil, and more specifically wet-clutches...a mainstay of motorcycle design. It is claimed that the new automotive motoroils have less protection for modern motorcycles engines and transmissions and can cause clutch slippage because of the new aditives being used.
In regards to our beloved CB750 SOHC, these motorcycles were conceived, engineered and used in an era of very non-specific engine oils, in other words - designed to run and perform using the available standard automotive motoroils of the time, the 1970's. I personally run Castrol GTX 20-50 in my 750 with no issues. But in light of my recent investigations for this article, I am not above performing my own unscientific test by using a motorcycle specific oil to see if there are any performance changes. A report on my experience will be forthcoming.

Below are several links to the most informative documents I found. I could find no research prior to the MCN article of 1994...which leads me to speculate that there was little reason to be concerned with this oil issue much before the early 1990's.

http://www.calsci.com/motorcycleinfo/Oils1.html
http://www.calsci.com/motorcycleinfo/API.html
http://www.calsci.com/motorcycleinfo/Consumables.html#Oil
http://www.motorcycleproject.com/motorcycle/text/motoroil.html
http://www.thegsresources.com/garage/gs_additive.htm
Motorcycle Oils vs. Automotive Oils - MCN article 1994

So, you've read all the articles...right? Ok so if you didn't, what does this all mean to you? In a nutshell it is this...

Always buy the viscosity recommended by the manufacturer...e.g. 10-40, 20-50, etc..

Be careful about the oil you buy. Like anything else, you get what you pay for. You don't have to buy the most expensive oil, but don't buy the cheapest either. And if you do decide to buy a "motorcycle" oil, then you have just eliminated making any mistakes.

Do not buy any oils that have the API "energy conserving" label, as these oils contain friction modifiers that are likely detrimental to your wet clutch.

Beware about buying "racing" oil. These oils are designed for race conditions and race DISTANCES!!! Let's see, I just watched the US MotoGP at Laguna Seca....45 laps, 2.5 mile course, hmmmm, that's 112.5 miles and time for an oil change...see what I mean! If you are racing your bike that's great..if you're not, BE CAREFUL.

And finally, Change your oil regularly. Motorcycles are hard on oil, especially air-cooled bikes. 2000 - 3000 mile changes will keep your engine clean and you repair bills low.