Couz wrote:I assume once I go synthethic its for the life of the car...right?
Not necessarily. You can readily switch between dino and synthetic oils at any time without any issues.
Couz wrote:Lesser intervals too.
Well, you have to be careful of that one. OCI's (oil change intervals) are going to depend on many factors. IMHO you should be doing oil analysis to determine how far you can extended you OCI's. There are many places that can do the oil analysis for you, ie. Blackstone Labs. This is how you would do this:
1) Select your brand of oil, then perform the oil change.
2) Drive, then change the oil at the factory recommended interval of 3750mi (6000km). This will ensure you flush all of the previous brand of oil.
3) Drive the distance you would for your extended interval. I personally do 6000mi (10,000km), you could do more but for warranty reasons I would not extend beyond Nissan's Schedule 2 Maintenence interval of 7500mi (12,000km)
4) Perform an oil change and collect an oil sample as per the testing lab's instructions. Usually you need to collect the oil as it's draining from the engine. Send it out for analysis.
Get your analysis results to determine if your oil was still in good shape. They should tell you lots about the oil including how much useful life was left.
A car driven short distances (less than 15-20min or infrequently) will not tolerate long oil change intervals. You risk shortening the life of the motor. In that case a quality conventional oil changed regularly is probably a better and cheaper alternative.
A car driven long distances (1hr+) would probably do well with 10,000+ km OCI's. Only an oil analysis will tell you for sure.