I posted this question in my 1st post, but figured I'd repost it as it's own question to get a little more viewing. For a late model Chevy pickup with the 350 minus two cylinders (also known as the 4.3L V-6), would a 15w-40 be a good choice? Engine goes through even 10w-30 high mileage stuff, and looking at the specs at manufacturers websites, it looks like Delo and Delvac have OUTSTANDING cold-flow properties! If it helps any, engine gets worked hard, sees a mix of city and highway driving, and has close to 90,000 on the odometer. I've been a Purolator user for years, but according to guys on this site, the K&N oil filter ($12.99 at Auto Zone) is far superior and thus the way to go. Plan on using either Delo and Delvac because of their superior cold-flow properties when compared to Rotella.