[whatthe]

I've seen some long term tests with Amsoil and Mobil 1 showing the oil was still good at 12-15k miles. There was a guy with a Camaro that sent the samples in at regular intervals even.

If you keep the oil in, just change the filter every 3k miles and you should be fine. The scariest thing about long interval oil changes for me is how the filtration abilities drop off over time if you don't change the filter. This will depend on what type of filter (i.e. depth type don't clog up quite as bad over time, but don't as high filtration capabilities early on).

I ran Amsoil to 20,000kms in one of my GTs years ago. The bearings looked brand new at 225,000kms after taking the engine apart to do some head work for turbo.

For Dino oil, I prefer Castrol.

If you do some google searching, you'll come accross lots of oil filter studies and oil studies to reference.