Oil Pressure

[muncieman]

I have a 65 Mack with an ENDTF673 Diesel in it. At 170 degrees operating temp the oil pressure is at 80 psi at the gauge. I think that is to high. Either my gauge is bad or I have an issue somewhere else. The motor only has 44 thousand miles on it as it is a fire truck. I was going to stick a gauge on it at the turbo to verify my fi dings before I do anything else. Can anyone give me a idea of what else could cause it. I'm guessing it has some type of relief valve and I was going to change my oil soon too.

[mechohaulic]

first started reading the post; was hit with "wall of confusion", the ENDTF  673 part. F was explained in following sentences. I agree 100% on your idea of faulty gauge and tapping another in system to verify first . did the high pressure just start? how long have you had this unit ?  did your change over to different oil ? ever do oil sample analyze?  side note :: what model truck ? 

[muncieman]

I've had it 3 years. It is a 65 Mack C85 fire truck. I have not changed the oil in it since I've had it, but will be soon.i have the service manual it says either straight 30 weight or 10W 40 or 10W 30

[mechohaulic]

also keep in mind; since that service manual was written :: mid 60's ==oil technology has changed drastically. hopefully others on here having vintage trucks/ engines will provide insight as to modern day recommendations for oil.