Oil viscosity

First of all, why are you running a mineral oil? That company makes a full synthetic. No way would I run a mineral oil. It's 2018 and it makes no sense.

Second, did you call the oil manufacturer and ask them what they want you to run? It's their products. They should know what you need and the correct oil to do it.

Third, what are your clearances? That makes a big difference is the viscosity you need.

Fourth, what fuel? If you are runny alcohol then you need to run a Group III synthetic (which isn't really a true synthetic) or a blend.

Fifth, what is the climate like? A 25 winter grade is only good down to about 35* F. If it gets colder than that, you may want to think about a thinner winter grade.