Mobil SHC 630 is what is currently recommended - see http://prevostparts.volvo.com/techni...df/MI99-08.pdf

PN 18217 from Prevost is $60. Graingers has the same quart size (all you need) for $20

http://www.grainger.com/Grainger/wwg...N=0&sst=subset

I'd say that you could use Delvac Synthetic gear oil 75W-90 which I have bought before at TA Truck stops

http://www.imperialoil.ca/Canada-Eng...vac_Syn_GO.pdf