Hemi Killer

iTrader: (6)

Kinda dumb question, but I figured I'd ask anyway. Can u mix the oil weight? I'm running 10w30 royal purple and since I install the bigger 34" radiator with a built-in oil cooler, the oil pressure has dropped close to 5psi and when it's hot it's idling at 30-35 psi. Motor is a 383 ls1 with a FMS ported oil pump. I've seen where royal purple seems to not run oil pressure as high as some other brands anyway.
I bought a bunch of the 10w30 and was wanting to know if it's ok to run 3 qts of 10w30 and 3 qts of 10w40 on the next oil change? I don't think you're supposed to, but thought I would ask. Would it give a little more pressure? Thanks.

FiredUpZ28

If your judging all of this from the cars gauge then I don't think you have anything to worry about. It probably won't hurt anything to mix the weights, but I don't think you have to.

LS6427

iTrader: (2)

So you have 200* coolant in the radiator trying to "cool" the oil? Hmmmmm.

You should use an external aftermarket oil cooler. Oil pressure is down because its too hot. Thats my guess anyway...........

and yes....mixing oils is perfectly fine. Just don;t ever mix different grade tranny fluid.

.

Darkman

iTrader: (2)

What size hose/piping did you run between the cooler and the engine? If it is too small for the distance involved the oil pressure will drop.

Hemi Killer

iTrader: (6)

I'm running the stock oil cooler lines, radiator and fan set-up from a 2005 silverado 2500. Everything was brand new btw. My truck is a99 silverado. I think the oil cooler lines are 1/2"...

Darkman

iTrader: (2)

How long are the oil lines from the engine to the radiator/cooler (approximately)?

Hemi Killer

iTrader: (6)

About 3 1/2 - 4ft can't really measure without crawling under it... Will get under it hopefully today

Darkman

iTrader: (2)

If it is 4 feet or less, and if it is truly 1/2 inch tubing the pressure loss shouldn't be substantial. As LS6427 mentioned above, oil coolers that are shared with the radiator are problematic simply because of their location adjacent the coolant that is presumably at 200 degrees F.

I would check the pressure with a mechanical gauge to make sure it is just not your gauge (sensor and grounds.)

If the problem persists, you might try disconnecting/bypassing or otherwise plugging the oil cooler plumbing to see if that helps. If it does, you could look at replacing the 1/2 inch tubing (equates to -8 AN) with some -10 of -12 AN.

In long run, you should not have to mix oils.

SAATR

Don't worry about mixing the oils together as you're not going to gain much, if any, pressure by blending them. Change completely to the 10W40 if you feel like you need it, but with 30 to 35 psi at hot idle, you're more than fine.