The math is really against you. Synthetics cost 3-4 times the price of normal dino oil and the most you would be able to safely extend the drain interval is 25-50%!!! If your car is under warranty, you cannot extend the interval at all without voiding it.
This is the 21st or so post on that specific subject, I believe, and the best way to get maximum engine life at the LOWEST OVERALL COST is:
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Use normal oil recommended for the engine.
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Change oil and filter at the recommended interval for highway driving in normal weather.
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For stop and go, and severe operation, drain oil every 3000-5000 miles.
If you do the above, your cost will be less than 1/2 of using synthetic and the engine will outlast the rest of the car!!!
P.S. This is all the review you need!