Big thanks to Mike Guillory who provided a good deal of this information
Energy-Conserving Oils
Energy Conserving (EC) motor oils may have "friction modifiers" which can cause clutch slippage. As such non-EC oils should be used for motorcycles with wet clutches. Look at the back of the container as it will clearly identify if it is an EC oil or not.
Synthetic or Conventional
Synthetic vs. semi-synthetic vs. "dino" oils. All motor oils have several special additives formulated into the oil to protect from corrosion and wear, plus detergents to keep combustion products in the oil. For normal (non-extreme) use, "dino" oils protect as well as the synthetic oils. However, if you plan to race, run at extremely high temperatures, or plan to extend oil-change intervals, or simply want the best, then a synthetic or semi-synthetic may be your best choice. It really is as simple as that.
Real World Test Results For Car Oils In Bikes
There is one good example in the June 1996 issue of Sport Rider magazine in a report called the "100,000 mile Honda CBR900RR." The owner used conventional Castrol GTX oil, 10W40 in the winter, 20W50 in the summer. He changed it every 4,000 miles, changing the filter every OTHER oil change. No valve clearance adjustments were required after the initial one at 16,000 miles. And a dyno test against the same model with only 6,722 miles showed torque and horsepower virtually identical. The 100,000 mile bike was even used for some racing. In a subsequent follow-up, the same CBR had passed 200,000 miles and was still going strong.
Other Questions
What is a reasonable oil-change interval?
Most manuals recommend not to exceed 10000km after break-in. But short-trip riding is considered severe service and the most common oil change interval is 5000km. However, a long trip is the easiest service for the oil and going 10000km between changes while on a cross-country ride is routine. Also, the use of synthetic oils can double the oil-change interval.
Will changing the oil even more frequently, like every 2000km, prolong the life of the engine?
Not likely, because at 2000km, the oil and additives are not degraded very much. Changing more often just wastes money.
What about the claims that motorcycle-specific oils contain "special polymers which are resistant to breakdown caused by motorcycle transmissions?
Oils usually require the addition of polymers, called VI improvers, to create a multi-viscosity oil, like 10W-40. Whether it is a motorcycle oil or an automotive oil, all polymers are subject to some degradation in the transmission. Full synthetic oils tend to have less polymer than conventional oils and therefore degrade less.
Why are motorcycle oils so much more expensive than automotive oils?
Cost of doing business is higher per liter of motorcycle oil. Large oil companies make so much more product that their profit margin per liter does not have to be so high.
What about the claims by specialty motorcycle oil manufacturers, that their oil is better?
Next time you hear that line, simply ask, "What evidence do you have?".
