John,
I ran Royal Purple ($5.00/quart)in my 250 Camaro and showed about 7% better gas milage. If the engine does not have loose rings and still has good valve seals it should not burn the synthetic oil. The biggest advantage to synthetic is less friction (better milage), doesn't break down as quickly, therefore you can stretch the changes. With the dirt from off road driving you probably don't want to stretch the changes though, so it might not be worth the added expense.
