25,000 miles or one year for oil changes. Amsoil ATM
Got it in my car, my truck, and use the motorcyle oil in my VTX.
Even use it in my riding mower.
Nothing better. Mobil One is good, but Amsoil is better.
They just came out with Signature Series Synthetic. It is good for 35,000 miles between oil changes. Synthetics do not break down, they just keep on lubricating. Just change the filter on a regular basis. They make a filter that is good for 25,000 miles.
Check it out.
Oh, by the way...my niece is still driving my old Accord. It has 265,000 miles on the odometer.
On my new car I use Mobil 1 Synthetic. Synthetic oil is vastly superior to conventional oil. It will not break down thermally like conventional oil and the only reason to change it is because it gets dirty. I knew an older fella that would drain his oil, change the filter, refill the car with the old oil and top it off with a new bottle. He would only use new oil once a year or every 4th oil change. I would not recommend that, but it worked for him and the car ran fine. Synthetic oil will not allow the internal engine components to wear. This is why you must drive a new car on conventional oil until the first oil change and then switch over to the synthetic. The syn. oil will not allow the engine to break in properly because of its anti-wear properties.
Also, it is beneficial to use in older vehicles for the same reasons mentioned above. Obviously its not as good as if it was used since the car was new but it will prevent wear from the time it is put in the engine. The only time I would not recommend using it is if you have an oil leak. The stuff is pricey and I would not want it just running out onto the ground.
Just so you know, I have over ten years of experience working in the auto parts industry so I have a good handle on this kind of stuff
Some people will tell you one brand of oil is better than another but their all basically the same, the important thing is regularly changing it. I think it really comes down to personal preference but my favorites and I would say the most popular are; for conventional oil I would go with Castrol GTX or Valvoline. For synthetic I like Amsoil but its hard to find and really expensive, its what most people use in their race cars, or what I use now in my mustang is Mobil 1, which is my favorite of the readily available synthetics. In reality you can't go wrong as long as you do regular changes.
But to answer your original question, synthetic is much better than conventional oil, especially if you plan on keeping the vehicle after it has over 60,000 miles.