keep using 20w50 were do you live?

 

So change it at 120,xxx, then again at 125,xxx, then 130,xxx and so on and so on.

 

i use 20-50 synthetic blend i want to use full synthetic but which one should use. i live in miami florida

 

Because you live in Miami stay with the 20w-50, switch to full synthetic, you will have use Castrol Syntec, that is the only full syn that I know of.
You could also use Mobil 1 15w-50. That is what I use in the summer.

 

is there much of a difference between the 15-50 and the 20-50 my wife drives it most of the time but when i drive it i have a pretty heavy foot i dont take it off road any more since i busted the front drive shaft

 

Well the 15w-50 will pump easier when cold then the 20w-50, but you wont notice any differance.
Both will give the same amount of heat protection.
Whichever one is more easaly avalible in your area is the one that I would use.

Now about your driveshaft, you are not driving around with it removed are you?

 

no i replaced it it went out the next day after i went off roading it just poped right off i bough an oem from ebay for 250.
dealer wanted 900 for parts