I am trying to cover few myths and practices adopted by local mechanics and give my logical answers based on my learning out of my 18 years of work with leading automobile manufacturers.
Do you know the chemistry of Motor cycle Engine oil is more complex than your Car? This is because of simple fact that Cars have different oil for Gear & Engine, whereas in Motor cycle your Engine, Clutch & Gear runs on same oil, which makes it more multi tasking & demanding.
Engine requires oil which is smooth & sustains multi grade lubrication; Where as Clutch needs a pinch of abrasive material to avoid slippage.
Myth No. 1: Sour Oil means Change? Apparently this is very close to chemistry, which indicates that oil is now more acidic than base. Fresh oil is base in nature & tasteless. Eventually when it looses its base nature becomes acidic (which is sour in taste) due to various reasons, primarily because soot and gases of combustion. However, what is the quantum of acidity in the oil is difficult to find out through tasting it. He may be testing his taste buds on wrong foot. Hence, better to go with the drain interval suggested by respective OEM. Also, don,t taste it as it always have very harmful chemicals.
Myth No. 2: Thick Black Oil means Change? The latest chemistry allows engine oil to retain dirt & soot within, to drain with engine oil & keep it clean. But again by seeing or rubbing on fingers its hard to determine that oil has lost lubrication. In fact the oil which is colorless in nature (normally with light golden color) would look more dirtier than the colored oil and experts claim that the lighter the oil, better it is in terms of properties as it indicates good quality of base oil (Group II)
Now thickness; You will be amazed to know that the thickness of oil changes with temperature, but exactly in opposite direction like other fluids which become thinner with rise in temperature and thick in cold state.
Engine oil specially (multi-grade oil) is developed to be thinner in cold state which helps them to reach quicker when Engine starts after halt; and thicker when Engine is in running state as than the requirement is to hold on liner for better lubrication.
So it is highly unlikely that local mechanic can check viscosity index just by feel of touch.
Myth No. 3 : Costly Synthetic Engine oils are best for Bikes: Straight No.. in fact it's always recommended to use engine oil recommended by OEM which in maximum Indian bike cases are normal mineral oil. Synthetic Engine oils are best suited for engines designed for them.
Myth No. 4: Engine Life Increases if you change oil before prescribed drain interval: Not really; as drain intervals are prescribed after intensive research & keeping safety of margin. Hence, it is not recommended until and unless your bike has gone through brake down maintenance and oil is getting changed with some part of engine, gear & clutch as exception.
About Writer: Hemant Kumar is holding 18+ years of experience in driving operations, P&L, multi channel product distribution and marketing involving both start-ups and growth organizations. Handled strategic positions for diverse automotive leading brands like M&M, Escorts, Anand Group, AMW Trucks & dealership giants as AML Hyderabad.