slowalty

i have a brand new rebuild in my 240 and got it runnin great and the oil light started flikering on. just at idle. so i hooked up a gauge and it reads 10 psi when cold. then i shut it down. but when you rev it up it gets good like 50. my buddy with an sr says this is normal. he says he run 10 psi when warm. im runnin 5-30. should i switch oil to thicker. or take it back to the machine shop. is this normal?