Genuine question: the only tangible benefit of using synthetic oil is longer oil change intervals -- if you stick to the scheduled oil changes, is regular oil just as good?
Sorry for posting again, but I figured that my last post was long enough.
I think using oil and changing it is the most important thing. Synthetic oil is better than crude in my experiences. There is less friction, you build up a lot less sludge and the synthetic oil stays more stable at temperature extremes. I don't know if you live where it's really cold in the winter, but regular oil really gets syrupy when the temps dip below zero. Synth stays much more fluid and makes for easier starting in the cold. Also, because you can get that oil flowing faster in the cold, you can get it up to the top end (valve train) quicker and consequently you have less wear.
The biggest cause of wear is cold starts. That's when the oil has drained into the oil pan and you are basically starting your car without any lubrication. That's why people say to let the car warm up when you start it and not to accellerate hard until it comes up to operating temperature.
The other advantages that I've noticed is that the synthetic oil is more resistent to "cooking". I have a '84 VW Rabbit GTI that I bought new. I used to run Castrol 20W-50 racing oil in the thing when new because I was always cooking the regular 10w-40 oil black within a few 100 miles or so. Someone turned me onto Mobil 1 5w-30. As soon as I put this stuff in, the car ran 20 degree's Celsius cooler (that's dramatic) and it was a lesser viscosity of oil, so it ran better. I never cooked the oil black after that either. I run Amsoil in my GTI today. It's negligable if it's better than Mobil 1, but I like to use it anyway because I believe that it's better. The car now has 180K miles on it and it's still running strong (compression numbers are way up there). Original motor, trans and even clutch. I never babied the car either.
I'll tell you were synthetic oil or fluids has made a huge difference for me. I usually have manual transmission cars. When it gets cold out, the shifter is usually stiffer than anything until the car warms up. When I switched to a synthetic trans fluid, the difference was amazing. The shifter never got stiff like that again in the winter and makes the manual box shift slicker than ever. If you have a manual transmission car and live where it gets cold in the winter, you'll know what I'm talking about.
One other advantage is that synthetic oil is far less likely to turn acidic when you leave a car sitting for extended periods of time. Regular crude oil breaks down into acids much easier and gets contaminated quicker when the car sits for periods of time. That's why they say to change your oil every 3K miles or 6 months (whichever comes first). I'd feel comfortable leaving a car sit for a year with synthetic oil, but not crude oil.
As you can see, I'm very pro Synthetic. In addition to actually working better, it's a lot "greener" too because you aren't using petroleum products. I also run at extended drain intervals, so I use less oil and that's definitely a good thing.
A tip: I will usually run my cars twice the recommended oil change interval with synthetic oil. What I do is run 3-4K miles with a fresh oil and filter change and then for my next change, I just change the filter and add up to a quart of fresh oil to top it off. The synthetic oil can withstand more mileage. What can't withstand the mileage is the filter. Regular filters should be changed every 3-4K miles. If you buy something like a Amsoil filter, you can run maybe 5-7K, but I never push it.
I think synthetic is worth it if you value your car. The only time that I wouldn't recommend synthetic is for something like a lease car or a car that gets driven casually on a regular basis, never sits and never gets driven hard.
Anyway..
Sal
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