no, seriously, i need someone with a little more experience to confirm what i am seeing. this is the first clean batch of oil that i've run through the truck, and its staying pretty clean. the history of the engine is questionable, but it doesn't knock or smoke, and it almost broke 13 mpg on my first real 300+ mile road trip, so i know its not in terrible shape.

i'm running 10w40 + 1/2 quart lucas oil stabilizer.

what i'm not getting is the oil pressure reading, its a sun pro mechanical (which doesn't really read below 20 psi). when i fire it up, pressure is great; about 70 psi cold. it slowly drops down as you would expect from the oil heating up and becoming thicker. at operating temp it hovers between 25-35 psi on the freeway at cruise speed, and at idle in gear it sometimes barely registers 20 (ie stopped in LA traffic). it definitely follows the 5 per 1000 rpm rule, and usually follows the 10 per 1000 rule. i'm not new to this, but never used the oil pressure gauge as a tuning tool (always just had idiot lights).

do i have bad oil pressure?
should i switch to SAW30 vs a multigrade? (I'm ASSuming SAE 30 was the original spec'd oil)
do i need more bacon?
how much oil pressure does a 460 generally like to see?

 

heck yeah on the bacon!!

carry on...

 

20 PSI at hot idle is OK. 35'ish at cruise is a little low but not dangerous. Lucas oil thickener does increase viscosity and can also introduce foaming.

I'd run it... maybe use 15W40 diesel oil or 20W50 at the next change and no Lucas. The diesel oil has enough zinc for a flat tappet. The 20W50 maybe. Run a zinc additive if not sure.

 

Try Valvoline ZR1 racing oil. It comes in 10w30, 10w-40 (although your local auto parts store may have to order these), 20w-50, which most stores carry and straight 60w.

This oil already has the added ZDDP in it so you don't have to add anything more.

As you engine temp goes up oil THINS, not THICKENS and that is why your pressure goes down. I have seen many engines idle at 20 psi and not have any problems.

If this is an older engine then clearances may be a little loose due to wear so a little heavier oil may help.

My last suggestion is to move out of LA

 

i don't live in LA, just have to drive through it occasionally. sucks, cause that city ruined a really beautiful patch of coastline...

i'm not going to put racing oil in the engine of a $300 truck. interesting you mention 20w50, cause i had a mix of that in the first flush and the pressure was lower. i'll try the ZDDP additive next time around, forgot that nothing comes with that anymore.

 

by the time you buy 'regular' oil and then buy the zddp additive, it costs just the same as buying the ZR1.

 

Oil doesn't really get thicker as it gets hotter. It get's thinner and that's why pressure drops. 5W30 acts like 5W when cold, but 30W when hot, but cold 5W oil is thicker than hot 30W oil.

Sounds to me like she just has some wear. High miles old school motor, maybe some wear, I like 15W40 or 20W50 in summer.

When cruising down interstate hot, with gas mashed and with gas let off in coast, is oil pressure same, or is it higher in coast mode?
If higher when in coast then mains have some wear as high vacuum pulls the crank up into top bearing shells where oil feed is .... while mashing the gas as in making power pushes the crank into lower shells away from feeds.

 

Sounds like you got loose worn main bearings ,Go to 20w 50 oil it should help .On your oil pressure gauge when you rev it up and then let off does oil pressure bounce up ? If it does you have loose worn main bearings

 

I would confirm those numbers with a different oil pressure gauge before condemning the engine.

 

yea, the engine is far from condemned. i'm probably over analyzing it, which is usually what happens when you give me a gauge.

i read this which got me thinking too:
Pirate4x4.Com - The largest off roading and 4x4 website in the world.

anyway, I'll see what i can find next on the next change. I'll probably try SAE30 and see what the gauge does. I'm sure its been a while since any ZDDP was put in so i'll grab some of that too.