sir this is what i came across and than decided to stick to owner's manual recommended grade....
Hope this helps...
"Most oils on the shelves today are "Multigrades", which simply means that the oil falls into 2 viscosity grades (i.e. 10w-40 etc)
Multigrades were first developed some 50 years ago to avoid the old routine of using a thinner oil in winter and a thicker oil in summer.
In a 10w-40 for example the 10w bit (W = winter, not weight or watt or anything else for that matter) simply means that the oil must have a certain maximum viscosity/flow at low temperature. The lower the "W" number the better the oil's cold temperature/cold start performance.
The 40 in a 10w-40 simply means that the oil must fall within certain viscosity limits at 100°C. This is a fixed limit and all oils that end in 40 must achieve these limits. Once again the lower the number, the thinner the oil: a 30 oil is thinner than a 40 oil at 100°C etc. Your handbook will specify whether a 30, 40 or 50 etc is required."
