I just bought an older Bobcat M500 to do a few odd jobs on my property, the person I bought it from said the gas filler was on the left and the hydro oil fill was on the right looking at the rear of the machine. I filled the gas and then the oil with 2 gallons of hydrolic oil and after about 15 minutes of running the engine started to smoke and loose power so it will not stay running anymore. At this point I'm thinking that both sides are for fuel, they both look the same but have no markings on them. I assume the oil filler is elsewhere, does anyone know for sure? The machine ran great for 3 hours prior to this.