a friend had a oil cooler thermostate stuck open. question would 2-3 hours running hard hurt the engine with hot oil. he currently has low oil pressure.

Oil Cooler thermostat?

A Lack of oil is causing a low pressure reading or a faulty circulating pump. Haven't seen an oil pressure thermostat yet. (Sending unit yes) An oil flow restriction is not a good idea.

I would think a stuck open oil thermostat would make the oil run cooler. The thermostat is to maintain the temp and warm up quicker..

Maybe you mean stuck shut?Cooking the oil reason the oil pres in low?

yes ,stuck shut no water flowing thru exchanger .oil was hot enough it smoking out of the vents in the valve covers.

dont know if he has 2 problems or if the the oil getting over heated compounded the low oil pressure problem . told him to change the oil and filter.

If it was stuck shut the oil broke down. I bet it turned to sludge .i would pull the valve cover and ck how bad it is. We had a company truck do this and the oil pres went to zero and started clattering . towed it back pulled the oil pan changed the oil pump and the bearings looked OK .Lucky .we shut it down in time .