Just got me a new 9.8 Tohatsu outboard and the owners man says use 10w30 or 10w40 with a chart for temps and so on, but i can only find 10w30 or 25w40 for outboards here localy. the temp cut off for 10w30 is about 86 deg and here in Tx thats about our low temp. Will the 25w40 be too thick even...