It's been quite awhile since I've been on this site and even longer since I posted. I got the "oil bug" tonight and I'm trying to learn. I've done a search on this site for the answer to my question and I'm frankly shocked that I didn't find a thread covering it. Maybe I didn't do the proper search procedure? Anyhow, my simple question is this: what is the advantage of using an oil weight beginning with 5W, 10W, or 15W, over a weight oil beginning with 0W? I do understand that, for example, there are more additives needed to make a 0W30 oil than a 5W30 oil, and those oils with a "bigger spread" will break down or shear sooner than oils having a "smaller spread". That being said, it would stand to reason that, in the identical application and environment, a vehicle using 0W30 oil should have it's oil changed sooner than the vehicle using 5W30, all things being equal. But the advantage of the 0W30 oil is that its viscosity at cold temperatures is less, allowing it to be pumped faster to moving engine components, presumably reducing metal-to-metal wear over time. I'm no expert here, this is just what I've gathered reading lots of posts and articles and based on some semblance of logic. If what I've said so far is true, then it would seem that the owner of a vehicle that recommends 5W30 should instead use 0W30 to prevent cold start wear and change his oil "somewhat before" the recommended mileage based on the oil having slightly less protection against shear and thermal breakdown, just to be on the safe side. My '83 Suzuki 650 air-cooled twin bike takes 10W40, so why not use 0W40 and change it out at 2000 miles instead of 3000 miles and gain the cold start advantages? My new Can Am Maverick Trail 1000 water-cooled twin side by side takes 5W40, so why not use 0W40 and change the oil every 40 hours instead of 50 hours? Now maybe there is no reason to change out a 0W sooner than a 5W or 10W oil -- that answer is for someone with far more engineering and chemical knowledge than me. From my own experience, I think much of when the oil is changed depends on the engine and how much "junk" it's putting into the oil, like acids and other contaminants. In power sports applications, especially air-cooled motorcycles that share the engine oil with the transmission (like my Suzuki), I think that oil will break much faster than oil in vehicles that are water cooled and don't have shared transmissions. With today's oil technology, oil changes in most vehicles are going way out there, sometimes over 10,000 miles. I'll tell you that with my '02 Bonneville (3.8L V6), that oil gets very dark brown in a couple thousand miles, and I use basic 5W30 in winter and 10W30 in summer and change it out well before 3000 miles. In my '07 Express van (5.3L V8) I can drive 5000 miles and the oil is a light brown. My point is, when an oil needs to be changed depends largely on the vehicle and the application. I'd like to know, why wouldn't almost every "enthusiast" go to a 0W weight oil, in every "non racing" application, unless they want to maximize the amount of miles between oil changes? I realize there are lots of people who want to buy the cheapest oil available, which will be 5W or 10W petroleum oils. I assume that most of the people on this site don't fall into that group. Thanks!!