what you need to know about oil...
Posted: Sun Mar 29, 2009 11:51 am
this guy knows his stuff. he's a member on another forum.
simon is the name, and if you look at my history and profile you'll see I was involved in R & D and Development in the bike industry for a looooong time. Worked for Honda, Suzuki and BMW, and several lube companies!
Oil is hygroscopic - that is it absorbs moisture (water) which is a recurring and fundamental component of metals that are retained in a room-temperature state. Over time, this water can be held in suspension by the oil, and where it comes into contact with metallic surfaces it can actually cause corrosion and erosion.
So the reason for regular oil changes (time, not mileage) is to remove these trace elements before they can do any damage to the engine internals.
There is a complex scientific document http://www.springerlink.com/content/k113gw42j3575327/
that explains this, but the simple explanation is that the only way to remove the water from the oil is to heat it up. Generally the only way to heat up oil in an engine is to start the engine, and as 70% of the engines wear occurs on startup and during warming, the damage is done. You cannot win by anything other than changing the oil!
Tthere are other long-chain molecules in oil that provide consistent viscosity and polymers that provide enhanced functionality and these also break down over time, especially in an engine that is not used.
For this reason, if you are laying up a bike for a long period, buy a few litres of cheap `dinosaur` oil (mineral oil, not synthetic or semi-synthetic), change the oil (and filter) every few months, and run the motor occasionally up to full working temperature (riding it is best, but a thorough idle for fifteen minutes every month will do) to keep the good oil circulated to all internal metallic parts. Also check the oil sight glass and look for a whitish `froth` sitting on top of the dark oil - that is the moisture, and if it's more than a mm or two thick after you've run the engine up and then allowed everything to cool, the oil is f*cked and should be changed at the earliest opportunity.
simon is the name, and if you look at my history and profile you'll see I was involved in R & D and Development in the bike industry for a looooong time. Worked for Honda, Suzuki and BMW, and several lube companies!
Oil is hygroscopic - that is it absorbs moisture (water) which is a recurring and fundamental component of metals that are retained in a room-temperature state. Over time, this water can be held in suspension by the oil, and where it comes into contact with metallic surfaces it can actually cause corrosion and erosion.
So the reason for regular oil changes (time, not mileage) is to remove these trace elements before they can do any damage to the engine internals.
There is a complex scientific document http://www.springerlink.com/content/k113gw42j3575327/
that explains this, but the simple explanation is that the only way to remove the water from the oil is to heat it up. Generally the only way to heat up oil in an engine is to start the engine, and as 70% of the engines wear occurs on startup and during warming, the damage is done. You cannot win by anything other than changing the oil!
Tthere are other long-chain molecules in oil that provide consistent viscosity and polymers that provide enhanced functionality and these also break down over time, especially in an engine that is not used.
For this reason, if you are laying up a bike for a long period, buy a few litres of cheap `dinosaur` oil (mineral oil, not synthetic or semi-synthetic), change the oil (and filter) every few months, and run the motor occasionally up to full working temperature (riding it is best, but a thorough idle for fifteen minutes every month will do) to keep the good oil circulated to all internal metallic parts. Also check the oil sight glass and look for a whitish `froth` sitting on top of the dark oil - that is the moisture, and if it's more than a mm or two thick after you've run the engine up and then allowed everything to cool, the oil is f*cked and should be changed at the earliest opportunity.
