It’s clear from your reply that I don’t understand how oil viscosity ratings work because that’s exactly what I thought. I guess maybe a blind hog just stumbles onto a nut occasionally because it sure seems like my engine is burning less of the 10w-30 than the 5w-30. Maybe at the next change I’ll go back to 5w-20 and see what happens.Okay but there is no such thing as a “0 or 5 oil” that’s not how the winter ratings work. The winter rating affects the pumping and crankability at low temperatures. Some 0W-30 oils are quite a bit thicker than some other 5W-30 oils except at temperatures below -35 where the two winter ratings become relevant. IMO it’s kind of unfortunate that the winter ratings use a number because it causes the confusion where people think it’s a “0” or a “5” weight oil and subsequently think it’s “too thin”. As has been already mentioned on here it would be better if a different designation was used such as a letter.