A follow up on my first post. I am ready to do the first oil change on my Z 2100 with the 26 H.P Briggs engine. Reading in my owners manual I see that 30 wt., 10W30, 5W30, or 5W30 Synthetic can be used. Never before have I seen such a wide variety of recommended oil weights for a engine. What oil have most of you been using?