|
Senior Member
Join Date: Feb 2007
Location: San Diego, CA, USA
Posts: 1,389
|
Oil Change Interval
Oil Change Interval
The oil drain interval that is specified in the owner's manual is for what is called normal service. Normal service is defined as the engine being at normal operating temperature, at highway speeds, and in a dust-free environment. Stop and go, city riding, trips of less than 10 miles, or extreme heat or cold puts the oil change interval into the severe service category, which has a shorter recommended change interval.
When the manufacturer gives a mileage/time criteria for oil changes they're telling you that if you drive every day, but (say) for only short trips to work, your driving habits put you into the severe service category and you should use time, not mileage, as a guide. So you may go 100 miles a week but do it in ten trips.
Motorcycle riding is often different. You usually ride for pleasure, but maybe only once a week outing for 100 miles, one trip (normal service.) So you should use mileage, not time as your change criteria.
Further, manufacturers are saying to change your oil even more often than the mileage interval stated in the manual because your motorcycle rarely experiences only normal service conditions.
The central dogma of motorcycle oil manufacturers and distributors has always been that motorcycles put different demands on their lubricants than do automobiles. In particular, they point to the facts that motorcycles run at higher temperatures and use the same oil in their transmissions as in their engines. The transmission gears supposedly put extreme pressures on the oil molecules, thus causing the long oil polymers to break down. High temperatures can have the same basic effect, as well as additional effects such as the increase in oxidation products.
When the size of the oil polymers decreases ("cut up by the transmission gears," as at least one manufacturer claims), the oil thins. In other words, its viscosity decreases, as well as its ability to lubricate properly. For example, what started out as a 40-weight oil could effectively become a 30-weight oil, or even a 20-weight, after prolonged use.
The viscosity of synthetic-based oils generally drops more slowly than that of petroleum-based oils in the same engine.
Here's the result of one test.
Castrol GTX, a non-synthetic car oil at 800 miles showed a relative viscosity of 0.722, meaning it had retained 72% of its original viscosity. Or, if you want to look at it the other way, the Castrol had lost 28% of its viscosity after 800 miles of use in the motorcycle.
Just for comparison sake, they also tested the viscosity drop of the same Castrol GTX oil after use in a 1987 Honda Accord automobile. At 3,600 miles of use, the Castrol GTX showed a relative viscosity of 92%.
So a motorcycle is definitely a more severe operating environment than a car so the oil change mileage interval should be shorter than for a car.
In the same test, since Mobil 1 car synthetic oil had retained so much of its viscosity after the 1,500 mile test, it was the only oil allowed to run longer in the motorcycle. After 2,500 miles, the Mobil 1 recorded a relative viscosity of 79%.
One more point. If you buy a motorcycle-specific synthetic oil it's no guarantee that you can extend your change interval. There were two motorcycle oils tested, Spectro 4 (petroleum based) and Honda HP4 (petroleum/synthetic blend). Both the Honda HP4 and Spectro 4 had lost over 30% of their viscosity at 800 miles, and over 35% at 1,500 miles.
So, because I ride infrequently for 200 mile jaunts - my choice - is to change my Mobil 1 15W-50 automobile-specific synthetic oil at 3,000 mile intervals.
Your mileage may vary, as they say.
|
Linear Mode
