Hi All,
I just did an oil change on my truck(360fe). I put in some Valvoline High Mileage Full Synthetic 10w-30 in her. I noticed that the already low-ish oil pressure before the change dropped even lower after the change. The oil pressure gauge in the truck now reads about a third up the gauge at idle, and doesn’t increase very much when driving. Below is a picture of the gauge when the trucks off(I should have gotten a picture when it was at idle/driving but I already dropped the oil to check it out, but there’s at least a reference for you guys when I say about a third up the gauge.) The other thing is that it takes quite awhile for it to build up oil pressure when I first turn it on. What should I do? Drop the pan and replace oil pump? Just keep flushing the oil? The truck was sitting for a while before I got it so the original oil was super thick so it makes sense that the oil pressure dropped a bit with some new stuff. It's still technically within the acceptable limits of pressure according to the gauge, but it's worrying that it takes a while to build up off of start and that it doesn't increase when on throttle. Thanks in advance,
Andrew

 

Welcome to FTE

As a general rule, the factory gauges are suspect. With something as important as oil pressure mechanics will use a separate old school analog type gauge plumbed directly into the block oil gallery for test purposes. These gauges are inexpensive, under $20 or maybe rent one.

Basically want to confirm that what you're seeing really is low oil pressure and get an accurate number, and not just a low oil pressure indication from possibly a wonky gauge or sender. It may well be the oil pressure is OK, or it may well have low oil pressure, maybe someone previously used a heavier viscosity and that explains the drop you're seeing. With hard numbers to work with though, you can decide what to do.

 

Thanks! Makes sense to do that. I'll look into it and see where I can pick one up and plumb it in before I do anything drastic.

 

Hey Andrew, I did some research a while back and found that a lot of people didn't recommend using synthetic oil on older vehicles.
The thought was that tolerances were higher back than and older vehicles have drier seals, etc. Since synthetic oil is a smaller molecule, it will find it's way through those areas.
Now I read that on the internet, so it has to be true, right?
Kidding about that. But I would be interested in your experience. Have you run synthetic before? Any new leaking that you noticed?
Just to be clear, I'm not pooping on your use of synthetic oil. Just interested in your experience.
I'm starting to think that not everything on the internet is true.
Thanks
Jeff

 

It is not just synthetic that can be a problem. The oil you just put in it likely has very small quantities of zinc. It meets the specifications for new cars, most of which have some sort of roller lifter setup. Low zinc on a flat tappet cam can lead to rapid failure of the lifters and/or cam. There will be others that chime in telling you that they never have had a problem with modern oils but some people have lost cams just during break-in on a brand new build. The risk is too high for me. There are a FEW modern oils that have high zinc - some for diesel applications but read carefully to see how much they actually have in the form of ZDDP. I just got a link to this yesterday from Speedway that you might find interesting.

If I was in your shoes, I'd put in some 30 wt high zinc oil and then measure your actual pressure with a separate gauge that others have mentioned. Make sure you are running a top quality filter as well. I tend to run Motorcraft and if you do some searches you will find others that work well.

Modern engines are designed to run full synthetic with very low levels of zinc. I haven't heard any convincing argument, other than from people who sell fancy oil, that a synthetic will perform and work miracles in an older motor. Since they oil tends to get contaminated more quickly in a carb engine, you need to change oil fairly frequently and fresh dino oil will perform well within the oil change intervals for older engines.

Just my opinion but I'd hate to see your posts in a few months where you are headed to a rebuild after filling the motor with fine iron particles from the cam and lifters.
https://www.speedwaymotors.com/the-t...m_content=hero

 

Tedster,

You mentioned "plumbed directly into the block oil gallery for test purposes". Could one put remove the sender and put a test gauge at that location? I was thinking about doing this since my oil gauge goes to about 3/4 immediately on start up and just stays there regardless of RPM or how long I drive for. Forgive this question, but is that the same as what you suggested?

 

I have been running Rotella T4 15w-40 oil in my 300 4.9L inline 6 for past 6 years with no problems. This oil has one of the highest amounts of zinc of the standard shelf oils. If your motor has a flat tappet cam & lifters you need a high zinc oil. Most Synthetic oil are made for roller cams & roller lifters. I would do some more research on oil before you run that synthetic in your motor. Just my 2 cents worth.

As for your oil pressure mine is just like "centennial f100", I have an original 1971 F250 oil gauge, when the engine starts gauge goes to about 3/4 and stays there hot or cold. If it was me I would try some 30wt like GPatrick said check oil pressure with a mechanical gauge before making any parts changes. Good luck.

 

You could add about 1/2 quart of this and see what your gauge reads.

Hobo

https://lucasoil.com/products/engine...oil-stabilizer

 

Yes, the sender fitting is perfect. The Amazonians used to have an oil pressure test gauge kit for under 20 bucks delivered. I am no expert, but after reading a little bit about oil pressure the general idea (generally haha) is to measure the hot oil pressure using the recommended factory fill. That's what the specification in the book is based on anyway, right? If the engine bearings are worn a higher viscosity than normally called for will help to raise the oil pressure some. This can prevent or delay those inconvenient uncommanded rod-through-block engine disassembly operations out on the highway.

But it doesn't necessarily follow that running say, a heavy 20w50 in lieu of the factory 10w30 oil is necessarily a very good idea in otherwise stock engine. If the factory-issue bearings are in good shape, if the pressure is within spec, then the factory recommended viscosity is going to be just about perfect for year round use in a wide variety of temperatures. It's crazy, I know, but it's almost like those Ford engineers that designed, built and extensively tested the engine and motor oils knew what they were doing. Almost.

In a rebuilt or overhauled engine it's a little different, because the builder can select or adjust adjust bearing clearances somewhat "loose". I sort of decided that the lightest oil that meets pressure specs is ideal, good fast flow at cold starts. That's why actually measuring the oil pressure and seeing what's what is important.

 

Thanks Tedster, That's my plan after reading this and other posts. I think my 90,000 mile 352 2V is original, but who knows for sure. I have the original "glovebox" Operators Manual and it recommends SAE 20W-40 or SAE 30 for temperatures between 32F and 100F. This is a spring to fall Sunday ride for me. I will check the pressure after a fresh oil change to make sure it is OK. I also plan to use a motor oil with zinc additive.

 

A full synthetic can also cause the piston rings to lose their seal to the cylinder walls. They lubricate too well for high mileage rings. I've seen it.

 

Thanks everyone! Super helpful users on these forums. I did buy a mechanical oil pressure gauge which I have plumbed from where the original oil pressure sending unit was to inside the cab. I also put a Zinc additive into the oil. By the looks of it, I may have just had a bad sending unit. The mechanical gauge reads just under 60 psi at cold idle, and drops to just below 20 at hot idle. So from what I've researched, that amount of pressure is just fine in a 360 fe. Thanks again for the help,
-Andrew

 

Just resurrecting this old thread with a question. My oil pressure gauge goes immediately to almost high on start up and doesn't move up or down from there when driving. I bought an oil pressure test gauge, as suggested, and connected it at the sender unit connection and got decent pressure. Warm engine, 600 rpm 26 psi, 2500 rpm 50 psi and 3000 rpm 52 psi. Is there a way to test the sender unit? If so I would like to try before buying a new one. In all likelihood it is a problem with the truck's actual oil pressure gauge, but wouldn't mind testing the sender unit if possible. Otherwise I could just buy a new sender unit and see what that does. At least I know from using the test gauge the pressure is not too bad.

 

No way to accurately test the sender. You can test the gauge without removing it from the panel providing your other gauges are working correctly. All the gauges work on a nominal 5 volts and 10 ohms high reading and 73 ohms low reading. If you can get a 10 ohm and a 73-ohm resistor you simply connect the resistors in place of the sender and turn on the ignition. + or- an ohm or two won't affect the reading. Using the resistors every good gauge I've tested lined up within a needle's width of the high and low marks.

 

Nice!

I just use a 100 (or 150?) ohm pot, but this is simpler!