Hello, I have a 36" metro fix 15 hp kohler and it is drinking about 11oz. of oil in 1.5 hours. The mower was only 15 months old when it started (after a oil change). Is this normal for and Exmark with a kohler powering it? Dealer looked at it once and said there was nothing wrong with mower and I should be walking in smoke at that rate. The mower does not smoke. The mower has about 450 hr. or so.