Oil Change Viscosity Mistake
I just spaced at the parts store. In the stack of 5w-30 oil there was one box of SAE 30, and without noticing, I bought it. I did not realize it until after I had already poured the required 6 quarts...
Forum Discussion
5W30 oil is actually 5 weight oil with an additive package. these additives are long strands of polymers that are like spaghetti.. As the oil warms, these long strands expand and make the oil thicker.. When your oil reaches operating temp you have 30 weight.. However as the miles add up and the oil circulates over and over, The long strands get sheared by the oil pump, making them shorter and shorter and lowering the oil viscosity.. Straight weight oil does not have this problem as it does not have the Multi-vis additive package.. 30 weight is the weight of the base oil, not 5 weight.. Therefore it does not have the shear problem and does not lose viscosity.. Years ago when I worked for a motor coach company we used straight 40 in all of our over the road diesel buses. We ran 15,000 miles between oil changes and had no problems.. It will break down eventually but you can run a lot farther between oil changes on straight viscosity oil..
