Ok, I'll join in the fun.
oil is oil and any oil is better than no oil have seen subarus run anykind of oil and last forever run it low one time and done
I basically agree with this. On a related point, I would say that for most people, the only real benefit of 3K oil change intervals is that someone looks at your engine and checks fluid levels more frequently; otherwise, it's a waste of money and resources. On most good running engines, you should go at least 5K miles. Some known sludgers have flawed PCV systems and/or other engine design flaws.
Valvoline... I've had timing belts snap & head gaskets blow (coolant issue) but I have never had any engine problems from using Valvoline. 25 years and counting...
I run 5000-7200 miles between oil changes. Just removed my engine at 270K and adjusted the valves, new timing belt kit, clutch, CLUTCH FORK (reason for all this preventive maintenance... ), Alternator (Go figure that one out???), and misc odds and ends... BUT under those valve covers were two heads that were nice, clean, and with a metal finish. No GUNK. I wish I would have taken some pics to show had I read this article previously...
I second the use of always using Valvoline...
I'm not brand loyal, but I do run longer intervals (average of 12K/1year) on my '99 Forester using various synthetics, only because they're usually blended with a better additive package and are less chemically reactive w/ combustion blowby. Consumption has been the same no matter what I've used: 1 qt./6.5K miles. Here are a couple of photos I took during a valve adjustment at 137K miles: http://s759.photobuc...t=ValveHead.jpg
An SAE paper found that oil temperature was most important in determining engine wear rates during warmup to operating temperature. The paper concluded that there was no appreciable difference in engine wear between oils of different viscosity or synthetic vs. conventional oils. In other words, an engine will wear the same (more or less) during the period of warm up to operating temperature no matter what you use, all other things being equal. Heat activates the anti-wear additives, which is a contributing factor. So it seams that the benefit of lower viscosity and low temp. flow of synthetics is less wear and tear on the starting system and better fuel economy during warmup as the engine doesn't have to work as hard to churn the stuff around.
Unless you actually need the resistance to thermal oxidation (read "turbo") or the lower pour point of synthetics at startup during winter, the only benefit of synthetic is that it gives you longer, not better, protection because it is not as chemically reactive to combustion byproducts and usually has a more robust additive package than conventional oils.
Edited by hohieu, 03 November 2012 - 01:10 PM.