It doesn't matter which type of oil you use. It won't increase your fuel economy at all. Full synthetic oil costs a lot of money and isn't worth it. I used it in one car I owned (for the entire life that I owned it) and there was no difference compared to any other oil I have used. I know people who only use synthetic and their engines are in no better condition than mine. The only benefits between different types of oil are the additives they put into it.
It is just like gasoline. All the gas comes out of the same pipeline the only difference between Mobil and Exxon is the additives added.
The only thing that I am sure synthetic is good for is that it stays thinner in cooler temperatures and will probably lubricate your valves and such faster than a conventional oil in winter. But when we are talking a difference of a few seconds, does that even matter?
'85 Dodge Lancer ES Conventional 118,000 miles (bought with 80K)
'90 Dodge Spirit ES Synthetic 168,000 miles (bought with 110K)
'91 Dodge Spirit R/T Conventional 110,000 miles (bought with 75K)
'97 Dodge Intrepid Conventional 103,000 miles (bought with 78K)
I have gotten the same amount of life out of each car I have owned regardless of oil type. The 90 Dodge Spirit was owned for 3 years and driven across country 8 times. The Lancer was dumped due to computer problems and not engine problems. The R/T doesn't use or leak a drop of oil at all.
So, when it comes down to oil selection, get what you want and what makes you feel good. Above all, make sure you change it every 3000 miles or every 3 months and it will be fine. JUST DON'T SKIP OIL CHANGES!!
