Best brands of oil

[Autotech]

Very true - synthetics are incredibly superior to conventional oils in terms of longevity. They also cost a lot more. And as I said earlier, they don't decrease the amount of blowby contamination in the crankcase, although they may reduce the amount of wear generated contamination. Also, most synthetics don't have a very agressive detergent package (most don't need it) - as proof of this simply put a high detergent conventional oil in an engine that has had a straight synthetic diet and see how quickly the detergent oil gets dirty.

Generally the O.E applications for synthetics specify long oil change intervals, as high as 15,000 miles. They get away with this by using large filters, and keeping engines spotless during assembly. Also, in these applications, engine temperatures are generally held below 200 degrees F. Unfortunately most domestic automotive product uses ridiculously small filters, and they hold engine temps at or near 210-215 degrees F (remember - the cooling fan and radiator, NOT the thermostsat determine ultimate engine temperature). If you feel inclined to use synthetics for these applications I would stick with changing the filter at 3000 miles and change the oil and filter at 10,000 - 12,000. Or better yet change the oil and filter every 3000-5000, although this gets expensive very quickly!

On my own vehicles I use premium grade convetional oils in the engine with frequent oil/filter changes (3000-5000 miles) to keep the level of contaminants under control, while in gear cases, transmissions, and differentials I use synthetics to take advantage of their superior longevity, flow, and shear strength.

[rbhollabaugh]

Even though synthtics are considerably more expensive I change the oils as per the owner's manual - sometimes sooner as I think the owner's manuals are more inclined to make service easier on the customer rather than better for the car.
Also recently switched to Mobil1 oil filters. Everyhting I've read about them indicates a superior filter element.
When I think what's cheaper - expensive oil changes or engine/trans rebuilds. Even though I would be the one doing the rebuild - thereby making the rebuild cheaper - It's still cheaper to avoid costly rebuilds by using oil that's slipperier (is that a word?).
Since I keep cars for 10-20 years I always think longer term than the usual car owner.
The car I drive everyday is 17 years old.

[chrisjbell]

I used to use regular oil in my car, but switched to synthetics on the advice of my mechanic (who services very high end cars - just BMW, Porsche, and Ferrari). Before I switched to synthetic I changed the oil and filter twice as often as the car told me to (it has a light system that indicates when service is required), which was about every 3000 miles. Now I change oil and filter according to the service indicator's recommendation (about 7000 miles), which with a synthetic I'm comfortable with.