Thread: Newb Oil Pressure question

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Originally Posted by techinspector1

... Install a new standard (not high pressure, not high volume) Melling oil pump. Bolt up the pan and fill with 10W-30.

Tech - Why not high pressure, high volume? (Not that he needs it with a mild mannered engine, just curious.) Also, why 10W-30? Why not 20W-50? I'm not trying to confuse the issue; my engine experience is limited and I'm curious about your reasoning.

Originally Posted by J. Robinson

Tech - Why not high pressure, high volume? (Not that he needs it with a mild mannered engine, just curious.) Also, why 10W-30? Why not 20W-50? I'm not trying to confuse the issue; my engine experience is limited and I'm curious about your reasoning.

I would like to read Techs answer also,but I'll bet it's because the high volume/high pressure pumps rob horsepower and wear dist.drive gears, all you are doing is pumping extra oil to the top end. All ya need is 10 psi for every 1000 rpm,"just a rule of thumb" and the stock oil pump is more than capable of that.

Originally Posted by J. Robinson

Tech - Why not high pressure, high volume? (Not that he needs it with a mild mannered engine, just curious.) Also, why 10W-30? Why not 20W-50? I'm not trying to confuse the issue; my engine experience is limited and I'm curious about your reasoning.

A street driven motor with a stock 5-qt. oil pan doesn't need high pressure or high volume. All that does is put additional strain on the distributor drive gear, cam drive gear, drive shaft, pump and ultimately the timing set at the front of the motor. Now, if a guy is gonna buzz the motor, then he's going to want to design the system with a bigger pan and more pump. Here's usmcdad's original statement....

"Last couple of seasons it seems our oil pressure is going south."

That tells me that BEFORE the last couple of seasons, all was well with the oil pressure. And that tells me that either he has changed the brand of filter he's been using and the filters are contributing to the low pressure (have read lots of bad juju about Fram in the past year) or the bearings are going away and bleeding pressure off or the pump has clearanced itself loose between the gears and the pump body or the relief spring has gone weak or the spring piston is sticking in its bore.

If all the mechanicals are correct in the motor, it doesn't need anything heavier than 10W-30. My old 300-6 Ford motor required 2 cans of STP and 40weight oil to get enough oil pressure to operate at all before I rebuilt it with bearings and standard pump. Now, I use 10W-30 with no additives except ZDDP and the pressure is 45-50.