Figured I would do a separate thread on this so others can search it in the future. I changed the oil recently to 10W-40 and noticed the oil pressure sits a bit on the lower end of the pressure gauge. When the engine is cold and I first startup and drive it is probably 3/4 up towards the high side, but once she warms up it wants to sit in the bottom 1/5th and doesn't really move much during cruise etc. I have some photos for reference here. I am taking the truck to Vegas where it is going to be quite hot outside and so am nervous about making the drive from Malibu to there especially with temps rising. Was thinking of switching to 20W-50 and seeing how this works out. Anyone running 20W-50 on these trucks? This engine runs great, but I think it is just an old tired farm truck engine. The previous owner had literally created an RTVd oil plug on this thing and there was a bit of sludge sitting at the bottom there when I changed it, so it must've been a while since it was changed. Oil filter looked fine though.

 

How was it before you switched and what did you use before. I wouldn't trust a 50+ year old gauge, put on an auxiliary if you're worried and really see what it's doing.

I use 10-40 and have great oil pressure

 

It was around the same spot. Just seems like such a huge swing from cold to hot on that needle, but I know these things usually aren't that trusty. Just ordered a mechanical gauge, will hook it up and see where the numbers fall. All my experience has been with small block windsor engines, so learning these FEs as I go. Appreciate the quick reply.

 

Have you had the pan off to inspect the oil pick up? I ask because I had a newer model engine in my daily kick the bucket after only 80k miles due to oil starvation. The car had sat for about 6 years and unbeknownst to me, there was significant sludge built up that ultimately plugged the oil pick up screen and starved the head of oil, wiping out a camshaft (this was a vw engine). If that all checks out, you might want to look at upping the weight or, keeping your current oil and adding a bottle of Lucas Oil Stabilizer. I always run 10w-40 and a bottle of Lucas in mine but its not driven much.

 

10psi per 1000 rpm is all you need.

You are good with the 10w40 or since you are in a warmer area, especially summer time, the 20w50 will work too.

As OEM 10w40 was probably one of the specs.

We used 10w40 in our '66 390--I got the ticking lifter to loosen up with some detergent additive and a new diet of 10w40 after the old, old 30w Delo my dad was using turned it into a clacker.

 

FEs are notorious for running with relatively low oil pressure, but the gauge you have really doesn't tell you what you have.

i run rotella t4 15w-40 in my 390 because its cheap and has high zinc content... the vr1 racing 20-50 would be a good oil too but it's obviously a lot more money.

 

Yeah the VR-1 is what I ordered, I am going to get a mechanical gauge on this first though and confirm where these numbers are at when I run it. I can then mentally note what the positions on the gauge line up with. If all checks out, will leave as is. Weather here is always 77-85 at the warmest so it would be fine. Having it out in 110 degree weather is what is making me more nervous about the oil viscosity. Worried I drive it to Vegas and oil pressure works its way down cause the engine runs warmer.

 

I run Rotella T6 5w40 never had a issue. I daily my truck year around. Winters it's in the single digits and summer its well over a 100.

 

I put the pennzoil higher mileage 10w-40 right now. Will check out some of these other options when I get the gauge on it and see what my pressure is at. Thanks for all the replies.

 

You are in luck, its not that hot yet in Vegas. Its supped to hit about 92 by Friday and drop back to the mid/high 80s next week. I run the 10/40 in Vegas year round and never noticed my oil gauge swing that much. It would be nice to have some better gauges though for oil and water temp at least.

 

Normal oil pressure should be 35-60 @2000 RPM hot. No off the shelf oil except Diesel oils and racing oils have enough zddp left in them to keep your flat tappet cam happy. Rotella T4 in whatever flavor you prefer would be a better choice than the Pennzoil since the T4 is intended for older Diesels with flat tappet cams.
What is ZDDP - Benefits of Zinc in Oil (speedwaymotors.com)

 

this is a great plan... when you look for a gauge, get one with the copper supply line. those plastic ones are a problem waiting to happen

 

So I cannot manage to get this oil sending unit off for the life of me and I have to make the trek to Vegas tomorrow. I decided to just throw the VR1 20W-50 so I got the extra peace of mind and the higher zinc content oil in there. Gave me a chance to flush this thing out a bit I guess. It did bump my oil pressure up when running hot on the gauge to where it is now 1/3 of the way up the arc when hot. Will have to tackle getting a mechanical gauge on there some other time once I am in Vegas.