Lope wrote:Neosophist: thats interesting. The tests I read comparing synthetic vs non synthetic were on taxi cabs, not motorcycles. On the cabs there was zero difference and in some circumstances the non synthetic even performed marginally better.
So there could be a point there about running motorcycle oil on a motorcycle.
I'd like to see the test if u can find it.
That test isn't really relavant though.. as your testing two types of car oil in a car, they also make synthetic oil for a car.
Though 4-cycle motorcycle engines may be considered more similar to automobile engines than 2-stroke motorcycle engines, they still have very different performance requirements. Historically, 4-stroke motorcycles have had problems with gear pitting wear in the transmissions and clutch slippage. In many cases, this can be directly attributed to the oil used. Most automotive engine oil is developed to minimize friction and maximize fuel economy. Since the oil for many 4-stroke motorcycles is circulated not only through the engine [as with an automobile], but also through the transmission and clutch, different characteristics are required of the oil. First, a certain amount of friction is necessary to prevent clutch slippage. Second, the oil needs to prevent wear and pitting in the gears of the transmission. These and other essential characteristics are addressed in the standards developed by JASO for 4-stroke engines.
As with the 2-stroke classification, the JASO 4-stroke classification is also divided into grades, MA and MB. MB is lower friction oil, while MA is relatively higher friction oil. Other than friction, the JASO 4-stroke classification tests for five other physicochemical properties: sulfated ash, evaporative loss, foaming tendency, shear stability, and high temperature high shear viscosity (HTHS). Sulfated ash can cause pre-ignition if the oil is present in the combustion chamber. It can also contribute to deposits above the piston rings and subsequent valve leakage. Evaporative loss and foaming reduce the amount of lubrication and protection in the transmission, engine, and clutch. With less shear stability, oil loses its capability of retaining original viscosity resulting in increased metal-to-metal contact and wear. High temperature high shear viscosity tests provide viscosity characteristics and data under severe temperature and shear environments.
A simple explanation from Mobile1.com
Answer:
Motorcycle oils and passenger car oils are very similar, with the exception of a couple of areas that are key to motorcycle operation. The first area concerns common sumps, or the use of motor oil, to lubricate and cool the transmission. As you know, in a passenger car the transmission is lubricated by an ATF fluid, which has frictional properties required for transmission operation. In a motorcycle, where the transmission may be lubricated by the engine oil, an engine oil that does not have the same level of friction modification (for fuel economy) of a typical passenger car engine oil will provide better transmission performance in terms of transmission lock-up and slippage. So motorcycle engine oil does not contain the friction modifiers of a passenger car engine oil. The second area of concern for motorcycle engine oils is that they tend to shear (breakdown viscosity) more quickly than a typical passenger car. Mobil 1 motorcycle oils are designed to provide exceptional protection against viscosity loss.
Basically, your car oils have 'friction modifiers' in them, these make the oil more slippy and improve fuel economy... most motorcycles have a wet-clutch that runs in the oil, these need a certain amount of friction else they slip with too much torque, car oil tends to make the clutches slip / wear out prematurly.
The second problem is the gearbox is very harsh on engine oil.. it sheers a lot of the additives added to car oil reducing the viscosity.. 10w40 becomes 10w30 in 1000 miles in some cases.
Just search the net for car oil in motorcycle, theres loads information about it.
A friend from a bikers club ran mobil1 in his VF750 interceptor for years telling me motorcycle oil is a 'waste of money'
His clutch, transmission and cams are all now badly worn and the bikes done half the miles as one of my VFR's.
He's not one to slack off on maintainance either so I dont think its just co-incidence.
Modern bikes are quite sophisticated, it's like me putting red diesel in a modern engine.. sure it'll run for a while but when the engine becomes all sooted up and brakes down i'll know why!
