What type/weight oil should I use in my 34 year old Kohler K301a?

I have been using Pennsoil SAE 10W-40, the 10w 30 seemed too thin.What type/weight oil should I use in my 34 year old Kohler K301a?
i have a 27 yr old Toro and the book says straight 30 wtWhat type/weight oil should I use in my 34 year old Kohler K301a?
Please do not use a multi-viscosity oil in a small engine! It is not designed to hold up to the increased temperature that small engines produce. So many people have been in my shop over the years with failed engines due to 10W-30 and 10W-40 oils that failed to lubricate properly, and factory warranty will not cover this type ';customer abuse';. Stick to the manufacturer recommendations, use a good 30W oil. It can stand the pressures of small engine life.
I would say stick with 10w-40 because that is mid grade.








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