I agree that we shouldn't waste lubricants! My statement was pointed against the use of 30 weight oils in the Duramax. It is just plain irresponsible to tell someone that "it's OK" to run the wrong oil, and that person is not the one on the hook if GM denies your warranty. The manufacturer of the oil does not stand behind a product not used as intended, and using a 30 weight oil in a application that requires a 40 weight oil is an example of a product not being used as intended.

I don't care what brand of oil a person uses as long as it meets the manufacturers requirements. The truth is that any major brand of oil will give you the protection you need. I personally use synthetic oils in all my vehicles, but I also know that I'm really wasting money. The best and only completely independent test of motor oils I know of was done by Consumers Union. They ran many vehicles a total of over 4 million miles under controlled conditions. There was no measurable difference in engine wear between drain intervals of 3000 and 7500 miles, and no measurable difference in engine wear between conventional and synthetic oils. Even knowing that I still prefer synthetic oils and will continue to do so as a personal preference. I drain at the maximum interval allowed by the manufacturer (usually 7500 miles). As many have discovered here through oil analysis the real reason we change our oil is NOT because the oil is "worn out", but because it has become contaminated with dirt and other contaminants. We change the oil to flush out those contaminants and replace the old dirty oil with new oil that is capable of maintaining the additional contaminants in suspension. No motor oil in the world can stop from becoming contaminated and extending the drain intervals too long just keeps those contaminants in your engine. Motor oils, at least the good ones, are designed to keep contaminants that are too small to filter out in suspension. These oils usually look "dirty" due to this desirable factor. Some cheap oils that look "clean" after a few thousand miles are not doing their job properly. An oil that fails to maintain the contaminants in suspension allows them to precipitate out and become what we call sludge.

GM is working in the right direction by getting away from absolute milage ratings for oil changes. The oil life monitoring systems are still in their infancy, but it is a step in the right direction and someday they will be extremely accurate in their determination of the need for an oil change.