I personally love the Shell Rotella T 5w-40 syn. I run it in every vehicle I own (XJ w/145k, Civic w/85k, Del Sol w/129k, and a Suzi 750 V-Twin with 26k). I started out with it just in my bike, because I had read it was great for wet clutches... It is. No slippage in a bike (and I do like to wring its neck from time to time!
) and my engines have always been rock solid in all 3 of my cars. I love the stuff. Once you get that first change out of the way (I did mine at 1500 on each vehicle to get any sludge out. There really wasn't that much, really) - I'm getting 5k, sometimes 7500k, depends on the conditions. If I'm doing a 10 hr drive to S. Florida, then I'll change it early at around 5. If it's just standard driving, I can let it go to 7500, and even then I change it because I feel guilty, not because the oil looks or feels broken down. People who say that syn is a waste of money don't realize that you can double your mileage between changes, once you have the interior of the engine clean and running well, and even when you figure a couple bucks more for the oil, it's not twice as expensive and I feel like I end up saving money in the long run.
BTW - sounds cheesy, but WalMart carries the Rotella T Syn (Dark Blue bottle) for $12 a gallon. Yes, that's $12 A GALLON - 4 QUARTS. That's the price of a good Castrol or similar conventional oil in most stores. I'll spend $3/qt on high quality syn anyday. Add in the double-mileage factor, and I feel really good about using a very high quality syn at half the cost of dino oil.
But again... as I saw in another thread:
Coke or Pepsi?
Regular or Decaf?
Less Filling or Tastes Great?
The world may never know....
I know what I use and I love it. Everyone has their own reasons and preferred brands. What I do know is that syn has beat conventional oil in every test known to the industry, and if cost is your main objection, then I think I've demostrated the cost-effectiveness I get from syn in my post!
Good luck, and let us know what you decide to do.