Discussion
Oil is tested at two temps and the ratings are given according to the flow rates acheived at each temperature. These are 0 degrees F (low) and 210 degrees F (high). The higher the number the thicker the oil at the test temperature. All oil companies refer to the manufacturers recomendations and will not specify the viscosity to use so its wise to follow what your manual says. Having said that going slightly either side of the recomended values - ie: 5w40 instead of 10w30 should not harm anything so long as you do actually change your oil on a regular basis. From experiance with a very high milleage 330 BMW I found the recomended 0w40 caused a little more startup rattling when cold and more running noise when very hot. Changing to a 5w40 reduced the cold startup noise and for some reason the hot running noise although I dont know why as the rating was the same. I did use different manufactures though as Mobile one is known to be very thin.
To sum up I wouldnt worry to much about yr oils so long as you dont stray to far from the recomended as its more important to change it regulary - like every 5K miles Id say! A friend of mine in the 200mph club has carried out tests on his motor oil after various periods of time and it does degrade with use although its still within tolerence near the recomended change frequencies but since he and I both ran very heavily moded bikes we changed it every 500 - 1000 miles and after a weekend of 1/4 racing. IL be doing my Monaro oil at the dealer service interval and half way through myself again, it peanuts compared to the damage it could cause since I am putting more stress on my lump than standard.
To sum up I wouldnt worry to much about yr oils so long as you dont stray to far from the recomended as its more important to change it regulary - like every 5K miles Id say! A friend of mine in the 200mph club has carried out tests on his motor oil after various periods of time and it does degrade with use although its still within tolerence near the recomended change frequencies but since he and I both ran very heavily moded bikes we changed it every 500 - 1000 miles and after a weekend of 1/4 racing. IL be doing my Monaro oil at the dealer service interval and half way through myself again, it peanuts compared to the damage it could cause since I am putting more stress on my lump than standard.
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