you should never mix regular oil with synthetic. it will harm your engine over time. i would go get everything flushed out then add either one or the other.
They can be mixed.
its the same for all vehicles for regular oil 3months/3000miles and for synthetic 6months/6000miles
its the same process as changing synthetic oil, except you use regular oil.
Yes you can.
Yes
You don't have to use synthetic oil for your Saturn Vue but synthetic oil is said to lead to better performance by the car. Check out this chart on different types of oil that can be used: http://www.synthetic-motor-oil-change-and-filters.com/best-oil/oil-change-saturn-ion-and-vue-ecotec.php
Refer to saturnfans.com for a complete procedure
Synthetic oil or a blend of Synthetic and regular oil is much better for your vehicle than regular oil alone. Synthetic oil is MUCH more expenshive. If you change your regular oil every 3 months or 3,000 miles I will be fine.
Synthetic. Turbos should always be synthetic.
3000 miles if using regular oil, 6000 if using synthetic. I use synthetic for my RSX-S, but regular would do for a base model.
Oil changes are always necessary. If you mean can you mix conventional oil and synthetic, the answer is yes you can.
Either as the choice is yours. If you use synthetic then extend the oil change interval by 2,000 miles.