Synthetic oils are more stable than convential oils. The reason you change your oil is because it loses it's characteristics and minerals that are added to help protect your engine. Over time and from usage they dissolve. Oil also gathers up dirt and un-burnt fuel. Have you ever noticed when you changed you oil how black it gets? That's from carbon deposits(dirt), and fuel. Finally, you can take convential oil up to about 250* before it loses it's viscosity, and synthetics, you can go up to about 300*. And to finally answer your questions. I would change your oil about every 5000 miles, and I would use a good filter. Try to stay away from the Fram filters, The orange one provides minimal protection, but their other products will be fine. K&N make good oil filters and Wicks? sp? make a very good filter. You can get a Wicks? from NAPA.
Sorry guys... I saw this thread and I just had to put in my 2 cents worth.
I work an awful lot with marine engines -- outboard in particular. Synthetic oil is worth every penny in my field. I have literally seen gearcases fill up with salt water due to a bad seal and, with synthetic, no damage was done to the gears or the shaft getting it back to dock. Remember, an outboard engine is going to run at 3,500 rpm's just cruising and it's running with resistance from the water -- lotsa heat going through a gear that is tops 4 1/2" in diameter.
Synthetic also has an innate ability to coat the parts and maintain viscosity in even the worse conditions. I would strongly suggest from my experience that, for the few dollars difference every 3,000 - 5,000 miles, synthetic is one of the very best things that you can do for the engine. I am not a chemist by any means, but many of the OEM's oils come from St. Rose Louisiana just a few miles from me. Each supplier engineers their own mixture and it is amazing what a huge difference there is between one brand an another coming from the same plant. All meet certain minimum standards, but the top brands are much more consistent with much tighter tolerances. Finally, full synthetics will not "age" as quickly as regular oils so, if your letting your car sit during the week, you will have a more consistent fluid with synthetic three months down the line than you will with standard oil.
As for the filters, there are two main suppliers that set the standard. Champion, which manufactures for some of the OEM's, and WIX. Both of them do a fantastic job. The media (the filtering stuff) that both of these companies use is really a tough standard to meet trying to source from anywhere else. By all means stay away from off-brands many of which are sourced from China. They may look the same but they have not developed a consistent method of matching Champion or Wix yet.
So, the bottom line from my experience is PLEASE use synthetic and either a Champion (OEM) or WIX filter. The few extra dollars are coating every major part in the engine.
To Drummer: Excellent choices. I know Mobil holds very tight standards. As far as K&N's filter I can only speculate. I do not want to post misinformation, but I doubt they manufacture their own filters -- they most likely source from Champion or Wix. Regardless, though, they certainly put out outstanding quality. If they are making their own in house (I would be shocked), I would still feel quite comfortable with their quality. If they are out-sourcing, from their record in the industry, I would also feel very comfortable that their requirements are dependable. It is quite likely they are sourcing through Champion or Wix and have agreed with them on particular PERFORMANCE standards. Either way... good choice.
As for Tim... I've never, ever heard of that. I think you're joking but I don't know everything... LOL. I do know that once you change to synthetic is not a good idea to go back -- but I've never heard of anything regarding a mileage limit to put better fluids in your car.
Stallion, after further research you are 100% correct. I learned something new. Here's what I found:
"the use of synthetic engine oils is not recommended for the "break-in" period. Its outstanding ability to reduce wear by virtually eliminating friction between moving components is not desirable for a "break-in" oil. Certain predictable amounts of friction are required for proper "break-in" of piston and piston rings. AERA does not recommend the use of synthetic engine oils for the first 5,000 miles of service."
Well done my man! I appreciate you stepping in before TimPryor received bad information.