Info on the mower - Yard Man riding mower, 12.5hp Briggs single cylinder, no oil filter, 1.5 quart capacity. If I remember correctly it's about 4-7 years old. I bought it about 3.5 years ago used. No idea what was in the sump the first year, but for the last two I've been using Valvoline Synpower 5W-30 with stellar results. The oil has been in there since November and is still clear. It's absolutely spotless under the valve cover. I'm considering Valvoline Maxlife Full Synthetic 5W-30 due to its better additive package. Between those two, what would be the better choice? Would one of them hold up better to the heat? Not considering other brands, and definitely not considering 30W. Also, in your opinion, is a yearly fall oil change (after final mow, before winter storage) a reasonable OCI? Thanks in advance.