Here, Take a Poke at Me

I keep reading here of folks advising others to use a heavier weight of oil to improve their somewhat weak oil pressure. I just 'taint a buyin' it; I think that this temporary cure is just a little bit near-sighted.

Now, admittedly, I’m no engineer, just a buck-toothed, greasy old farmer, but consider this:

The very last thing to reach operating temperature within any engine is it’s oil and this can often take up to an hours operating time to fully reach it’s full operating temperature.

Have you ever drained that 175W rear end lube out of a tractor that has been pullin’ hard in the field all day? Ever drain the third members of 80W-90 on a semi-tractor that has just came in off a 12 hour run up the interstate pulling a load of cement? Ever drain the engine oil or rear-end oil on your own road vehicle after it is up to operating temp (not water temp, oil temp)?

They all have one thing in common; that used oil always drains out of there with the same consistency of water. It is just some pretty flimsy stuff.

Using a higher weight oil my bump that oil pressure in the short term before the oil actually gets hot, but I wonder if it really has any effect at all after we are warmed up and running good. Aren’t we really just puttin’ on a band-aid here?

Ya’ll have a good day,

Allan

I run M's on my farm. When I switched to 20w50 from straight 30w I saw very little pressure change in the good engines. Those like a '39 I have which is well worn and used lots of oil showed and increase of maybe 10 psi when it was hot. When it was cold, the oil acts like 20w so oil pressure was still at the relief pressure on the pump. The 20w50 significantly cut oil consumption.

I agree it is no substitute for an overhaul but I don't have the time or money to fix what ain't broke and if a band-aid holds it, I'm happy. I use Barr's Leaks in radiators that leak for the same reason.

I agree whole heartedly with Allen’s band-aid analogy of using heavier oil to bolster oil pressure. Doing so probably will cause more harm, and may mask more severe problems such as worn bearings, leaking oil pump gaskets, or warped or worn oil pump parts. Before putting in that heavy oil to bring up lackluster oil pressure, ask yourself these questions:

1.) Is the weather so hot that I don’t feel comfortable using a multi-weight oil such as 10W-30 (viscosity of 10 weight on start up, 30 weight after oil reaches operating temp).
2.) Is low oil pressure the only reason that I’m adding heavier oil? Oil pressure at idle above 25# hot is sufficient for any engine I’ve ever seen.
3.) If the answer to #2 above is yes, do you really want to take the chance that the oil pump is not the problem?

If you still want to put in that heavy oil, consider what might happen in the future if you do. If the oil pump has a bad gasket or is worn, lack of oil will cause premature bearing failure. This could result in having to tear down the engine, grind (or worse yet replace) the crankshaft and/or possibly connecting rods and if left go long enough replace the camshaft and lifters as well? Worst case is that the bearing will seize on the crank, snap the connecting rod and toss it out the side of the block. Hmm…

Sorry to sound like a lecturer, but bad oil pressure is caused by a problem somewhere in the engine. My “M” once had bad oil pressure, almost nothing at idle, and half gauge at full throttle warmed up. I took the pan off and found a bad connecting rod bearing. I got by with a .010 crank grind and new crank and camshaft bearings. (While I had it apart, I re-built the whole engine, but really wouldn’t have had to do the pistons and rings.) Think about the old addage "A stitch in time saves nine."

Lecture over.

That ain't a lecture; that is just plain good common sense.

If that oil pressure is down, it sure isn't being caused by the oil you're using, that's for darned sure.

The symptom that just literally screams "fix me", is the good oil pressure cold, bad oil pressure hot.

This engine needs opened up and there just is no way around it, because the very next step in the progression of events is then bad oil pressure both when cold and when hot.

Allan

20w50 is not a fix for a bad bearing but with moderate engine wear, changing to 20w50 can extend engine like by offering better oil pressure to keep loose parts lubricated.

It is true that 20w50 can mask only one bearing dumping all the oil but even 50w hot oil will not show good oil pressure in a very worn engine.

So, that's it!!

That's why people are always telling me that I look like the north end of a south-bound horse..... never knew what they meant 'til now! :>)

Allan

Okay. 90W gear oil at 210 F falls in the same viscosity range as 40W engine oil at 210 F. So I'd say that your observations are about right. Since 40W oil at 210 degrees is 1% as viscous as 10W at 0 F, all hot oils would look about the same as they drain out.

50W is about 3 times as viscous as 20W when they are both at 210 degrees, so it would take more force (pressure) to push it through long drillings and tight spaces in an engine. That would show up as higher oil pressure on a gauge. It actually works that way on my Super C, but the motor still needs a rebuild.

Hey!, are you the same guy that thought that ice didn't float ?

Greg

Yes, ice wouldn't float and all the pigs all flew. And, that ain't the half of it; when did the sky turn that pretty shade of blue, anyway? :>)

Say now, it takes quite a bit of my time to reason all these things out, ya know. Looks to me like you guys could be just a little more appreciative for all my efforts! :>)

Have a good one,

Allan

Not so darned fast! I haven't finished practicing my falling down routine just yet! :>)

scotty