I think you may see some efficiency with the synthetic oils, but I doubt that you'll see any MPG change...or not enough that it would justify the switch for that reason alone.
I like it, because I can do a single oil change a season in my cars, with the change at about 7-10K miles instead of 3-4K miles. But, with the oil costing about twice what the "dino" costs, there really isn't much savings there either....other than my time.
Some people swear by one oil over another.....just like you'll find the Chevy/Ford/Dodge camps on these forums too. That isn't to say that any of them are wrong...they just have a different opinion than some others do.
If you can get a good deal with some synthetic oil on sale, why not? You may find that your temperatures are a bit lower, and the engine my get a bit better performance, but don't count on it.
The whole secret with any oil, is to make sure you are changing it before it has to much dirt suspended in it, which would effect the engine. New cars and trucks are telling you to change the oil at almost 10K miles, but I'd still feel more comfortable cutting their number in half.
