Oil pressure question.
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Senior User
Joined: Sep 2009
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Oil pressure question.
Here's the issue I have a 1984 4.9 that I've installed a DUI new single barrel and motorcraft oil filter and changed engine oil to 10w30 and Lucas oil treatment. Had a manual gauge installed and had 7-10 psi on idle and like 40-50 running down the road. Issue is I installed the dash gauge and it flops to LOW at idle and normal while running but any stops it comes back to LOW. Any suggestions. I think I'm going to put 15w40 in the truck tonight and try it and see if pressure increases at idle. Any other thoughts?
Fleet Mechanic
Joined: Nov 2002
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That pressure does not seem surprising for a a 33 year old 300. That is sufficient oil pressure that I would not be afraid to continue driving it.
I race 300 ci powered dragsters. Because the oil pan is so long I lose oil pressure on every burnout - drops to ZERO - and at the end of every run - drops to zero after approaching 7000 RPM. I have come to think that the amount of pressure is more than adequate for a typical truck engine that rarely sees 4000 RPM.
I race 300 ci powered dragsters. Because the oil pan is so long I lose oil pressure on every burnout - drops to ZERO - and at the end of every run - drops to zero after approaching 7000 RPM. I have come to think that the amount of pressure is more than adequate for a typical truck engine that rarely sees 4000 RPM.
Junior User
Joined: Oct 2015
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From: Southwestern MO
The 300 in my truck has about 20 lbs of oil pressure @ around 2800 RPM. It drops to zero at idle, but has no noise. I use 15w40 Walmart Supertech oil in it. I have driven it about 50,000 miles like that. I have no idea how many miles were on it before I put it in the truck, it was rebuilt sometime in its life because it has .040 oversize pistons in it. The oil pressure on mine used to worry me too, don't trust the dash gauge!
FTE Legend
Joined: Nov 2015
Posts: 30,912
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From: Angier, NC
BTW they say 10 PSI for every 1000 RPM
Dave ----
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