'93 300ce

Just before I put my 2000 SL500 with 128k miles up for its winter nap I did an oil change, with mobile 1, 0 - 40 weight because last year I experienced tappet sound during spring awakening start. After driving the the car for a while the tappet sound disappeared. My hope was that this year the tappet sound would not recur but it did during todays spring start. My questions are: Is there a way to prevent the tappet from leaking down?, What kind of damage could this mean? The oil is changed once a year and oil consumption is negligible should I change to a different weight oil? Our outside air temp today high of 52 low 36.