he most important aspect for ensuring great performance and long life of engine of any bike is Engine Oil. Engine 0iL is to bike is what blood is to human. The quality and quantity of engine oil matters more than anything else in the bike. Therefore engine 0iL is the most critical maintenance aspect of any bike. The quantity and quality of engine 0iL to be filled is different for each bike model and is given in the OWNERS MANUAL of the bike. Read it carefully and follow it exactly. The procedure of changing engine 0iL is as follows:
Put bike on main stand. Keep a tin can or plastic mug exactly under the drain plug (which is at the bottom of the crankcase). Open the drain plug and let the old 0iL drain out into this can / mug. Keep the drain plug open overnight and let the old 0iL drain out overnight==many hours, so that last drop also drains out. Then in the morning measure and fill the exact quantity through the filler hole which is at the top of the crankcase. Before starting the bike, check whether the engine 0iL is up to the required level. Most bikes have a dip-stick attached to the filler cap, on which the maximum and minimum levels are marked. So measuring the level is very easy and convenient. However some bikes like Hero Honda Glamour, Suzuki Zeus and few others have a transparent inspection window (no dipstick) way down in the crankcase, and it is extremely inconvenient to check 0iL level. For one, a person has to almost lie down on the dirty ground to be able to see it and for another, there is never enough light to be able to see the 0iL level, more so in the bright sun!

For best results, after draining out the old 0iL, it is better to clean the crankcase by flushing it with flushing 0iL. If flushing 0iL is not available and / or too expensive, you can use ordinary diesel. To flush, what you have to do is as follows:

After the old 0iL is totally drained out overnight, next morning fill one litre of diesel in the crankcase. Put bike on main stand such that rear wheel doesn’t touch the ground, and start engine. Let engine run (bike on main stand) in neutral for 20 seconds only. Stop & switch off the engine. Let it cool for five minutes. Start again, put in first gear and run it for 20 seconds. Rear wheel will turn. Let it turn. Again stop engine for five minutes to let it cool, and do same in second gear. Repeat this process of put in gear, run for 20 seconds, stop engine for five minutes and run engine for 20 seconds in all gears. Then when diesel is still hot, drain it out completely, keeping drain plug open for at least 20 minutes. Then fill fresh 0iL. It is best to change 0iL filter every time you change 0iL even if it is synthetic 0iL.