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Joined: Oct 13, 2007 Posts: 26 Location: Richmond, VA, USA
Posted: Sun Nov 27, 2011 7:14 pm Post subject: Oil grade
So, I've gotten my KZ ready for the road. I changed the oil yesterday, but didn't look at the labels closely enough. I put in 10w30 instead of 10w40 (the first grade listed in the manual). I just got this thing not too long ago so I thought I'd go with synthetic -- I put in Mobil1.
What's the real effect of going with 10w30 instead of the recommended 10w40?
Joined: Dec 26, 2007 Posts: 1283 Location: Scottsdale, Arizona
Posted: Mon Nov 28, 2011 6:47 am Post subject: Re: Oil grade
Doug wrote:
What's the real effect of going with 10w30 instead of the recommended 10w40?
Doug
The real effect? Lubrication film strength at high operating temperatures of an air cooled engine. If this were 1995 instead of 2011, I'd say that the 10W30 would be fine as long as the outside temps didn't go above 80 degrees or so. But today's car oils are a lot different than back in '95, and that Mobil 1 10W30 contains friction modifiers intended to increase fuel economy. Unfortunately, the modifiers also increase clutch lock up time when used in a bike that shares the engine oil with the clutch and transmission - similar to the effects of putting STP in the oil, but to a much lesser extent. That slower lock up tends to increase the wear rate of the clutch friction discs and can result in premature clutch slippage due to worn plates. This issue is what created the market for motorcycle-specific oils. The problem mainly affects bikes with higher horsepower and torque output, so you may not have a problem. But I wouldn't use any 10W30 again, unless it's labeled as a motorcycle-specific oil. 10W40 and heavier car oils (no energy saving "starburst" on the front of the bottle) contain little if any modifier and present less of a risk.
For future reference, if you're going to spend that kind of money on oil, you may as well get an oil that meets JASO MA specs for wet-clutch motorcycles. The least expensive oils that meet that spec are actually a heavy duty fleet oil (some call it diesel oil) - Shell Rotella T 15W40 or Rotella Synthetic 5W40. Mobil 1 makes bike oils, but they're priced around $9/quart. A lot of auto parts stores sell Valvoline 10W40 and 20W50 bike oils at reasonable prices that claim to meet JASO MA specs. And of course, you can buy bike oils in any bike shop at prices up to $15/quart.
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Actually Stu, that was very complete and concise explanation of a complicated subject. Lets just leave it at that. 
