I have a Grasshopper 928D2 with a Kubota diesel D1105. The manual lists an oil filter part no. 100805 and recommends engine oil 10w-30 with a CD grade or higher. I went to NAPA today and could not find what oil filter I needed and they only sold diesel oil 15w-40. Can anybody help me find an alternative oil filter (other then Grasshopper), and do you know if 15w-40 will void engine warranty or do harm then Grasshoppers recommended oil of 10w-30? Thanks for any input.