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What affects oil pressure?

1460 Views 6 Replies 6 Participants Last post by  n0alpha
I only have this car in my possession for the past 3 months. I have observed that sometimes, during idle at a stop light after the engine has warmed up, the gauge reads at 2 and when I drive, it goes back to 3. When I start the car in the am and during idle, the gauge is at 3. Is something "stuck" causing it to be at 2 during idle at the light after the motor is warm? Or is this normal? It also sometimes "twtiches/bounces" back and forth around 2 a couple of times and then settles at 2.

The car had a valve job 18k mi ago. The rings were supposedley (sp?) checked during that time.
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First of all you have to consider the oil pumps position, in a 190 the oil pump is in the timing cover, this is an aluminum cover so its going to change dimensions alot faster due to temp changes, in the 560 it has a conventional cast iron oil pump that is in the oil pan. It is going to be alot more stable.

As long as the lifters are not making noise at idle, I would say that you have enough oul pressure. If you are in doubt, you can hook up a mechanical gauge. Rule of thumb is 10psi of oil pressure for every 1k RPM, so anything at 15 or more at ilde is enough, but keep in mind this is a "rule of thumb" its not written in stone. If you are not comfortable with the oild pressure, get a new set of rod and main bearings.... provided there is minimal crankshaft wear, that will increase oild pressure.
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