I have a BX 2200 diesel engine - 2004. Manual says 10W-30 or 40 with CD, CE or CF API. Could not find this API rating at my local farm supply store. All they had was 15W-40 diesel oil. I have owned my tractor since 2004 and have changed the oil regularly; however, I have always used 10W-30 motor oil and never knew to check the API - neighbor recently pointed out the API ratings. Have not had any problems, starts great in Chicago winters, but want to use the correct oil now I know about the CD, CE or CF. Any help greatly appreciated. Closest Kubota dealer 1 hr away. Thanks