Synthetic vs non-synthetic oil given car mileage

[dobrinov]

Please disregard this post as accidentally the thread posted twice, and I am not sure how to delete the redundant thread.
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Hey guys,

I can not find a thread when we discuss what is more appropriate type of oil to use given what the car mileage is. My specific questions are:

1. Can I use synthetic (e.g. Mobil 1, 7500 or 15000) in a 2.2 5s-fe (1996) with 150,000miles on the odo?
2. Are there (or WHAT ARE?) any advantages in using synthetic versus non-synthetic besides the not so frequent oil changes? In particular does it add to securing longer life of your engine, and does it help gas mileage?
3. Are these Mobil 1, Castrol and such oils that say they are synthetic on the tube really synthetic? If they are only 10-20% synthetic, is it still harmful to the engine to use when mileage is more than 150,000m?

My concern comes from the fact the Toyota's manual that came with the car says it is not good to use synthetic when the car is brand new and when the car has lots of mileage. I still want to see what is the opinion of the experienced Toyota drivers here.

If this issue has been discussed, please point me to the thread so I do not waste everyones time here?

Thanks
nick

[Dr Thunder]

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[RningOnFumes]

Dr. Thunder, this thread is a double post. The orignal thread can be found here: Synthetic vs non-synthetic oil given car mileage MODS, PLEASE DELETE THIS THREAD?