The full synthetic oil is the same price as the semi-synthetic around here and the semi-synthetic is hard to find.
Aside from that I don't think that there is any difference at all.
The G5 is the first vehicle I've ever put any form of synthetic anything in.
Personally I think it's a waste of good money. But then there is the warranty period to satisfy
CJ
Au Contrere' mon Frere'! Full synthetic lubricants are QUITE essential in a modern, high-speed, high temperature engine. One must understand the characteristics of dinosaur oil to understand WHY synthetic lubricants are required - AND "the bomb". First there is lubricity over temperature. Both oils in the same viscosity start out equal - and stay pretty much that way to about 180 degrees in oil temperature. The synthetic is fine - but the dino oil starts to lose its ability to lubricate due to temperature shear - that is the molecular structure starts to unravel. As the oil gets hotter and hotter, the dino oil shears more and more until at about 210 degrees with most oils, you start to have METAL TO METAL contact due to the oil being completely sheared. Meanwhile the synthetic is still good due to the fact that its molecular structure has been engineered with long chain molecules that actually clump together under heat and pressure making the oil have a GREATER shear strength than at lower temperatures! I've temp gunned the bottom of the UCE after a "brisk" run and gotten 220 degrees on the OUTSIDE of the oil plug ......
Another benefit of the synthetic oil, in the same vein, is its ability to resist "coking off" or turning back into car tar in your engine at temperature, Dino oils WILL coke off at about 250 degrees - put some on a hot plate and watch it! At the coke temperature - not only is the dino oil allowing metal to metal contact - it's actually turning acidic and ABRASIVE as it cooks into coal chunks. The synthetic oil, although starting to lose lubricity ( but only about 40%) will not coke off until about 380 degrees or so (all that depending on the blend and manufacture of the oil, of course!) - and at THAT temperature - you got more than hot oil!.
Look on the SAE.org website for info and read "The Practical Handbook of Machinery Lubrication" by Leunger. This is the bible of machinery lubrication of ANY kind - I have worn out a copy of it in my travails to keep everything from absorber pumps to stock car motors together. Bottom line, CJ - you ain't wastin' your dough - but you'll waste your little thumper if you put Quaker Cake into it .... !