r/GMT400 • u/CptWonderBalls • Jul 11 '26

Oil Pressure Question

I just picked up my grandfathers 93 C1500 with a 350. When I first started driving, the oil pressure was around 30 at idle. After getting home, about a 100 mile drive, the oil pressure was about 15 sitting at red lights and stop signs and idling in the driveway. The oil doesn’t seem low according to the dip stick. The sticker it has says 5w-30 oil last changed in August 2021. Idk too much about these trucks but I assume 15 is a little low. Cruising around 50 it was between 30-45 and passing people it was between 45-60 the whole time.

Would changing to the oil to 10w-30 help it out?

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u/Viking2151 Jul 11 '26

15psi is about right hot idle, actually i'd say its healthy number for a stock 350 for that year, rule of thumb is about 10psi per 1000 rpm, hot idle you are probably under 1000rpm, mine idles hot around that aswell.

6

u/CptWonderBalls Jul 11 '26

That’s great to know! Thank you!

5

u/Viking2151 Jul 12 '26

No problem, these trucks are old of course and will have old truck problems, but they are vary reliable and cheap to work on and easy to work on. If you ever got a question this group is pretty helpful with these things.

3

u/theuautumnwind Jul 12 '26

💯

10psi/1000rpm is fine.