I'm having trouble finding 15w-50 Mobil 1 Synthetic to use in the hydro system in my Exmark Hydros (Lazer and HP). My local auto parts store doesn't carry it anymore and the one other place that I know of that did carry it - was charging about $9/quart. Does anyone have a good alternative for the Exmark Hydro systems? I know that Exmark reccommends Mobil 1, 15w 50 but..... Any input is greatly valued. I know that you guys know your sh#t here and I really value your opinions.