Low oil pressure makes me nervous

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dibbons

dibbons

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La Paz, B.C.S., Mexico
On a road trip now '72 318 auto. Changed out my Castrol high-mileage 25W-60 wt. (not really available in the USA) for straight Quaker State 40 wt. before I left La Paz, Mexico. With the 40 wt., factory oil pressure gauge reaches the second graduation (near the center of the gauge) when cold (40 PSI?) but drops to the first graduation when warm (20 PSI?). Driving north up the Grapevine on Highway 5 in California this week, the gauge dropped to halfway between zero and the first graduation (10 PSI?). I was waiting for the motor to freeze up but it just kept climbing the grade and the pressure went back up to the first graduation on the way downhill. I continued another 300 miles to my destination to where I am now (Mill Valley near San Francisco). After a search, I found the 25W-60 not available in California at Napa, Autozone, nor Oreilly's). I just ordered online some Castrol 25W-60 online for my return trip and hope to get the oil pressure up a little more.

The good news is I am averaging 16-17 MPG in a 1972 Satellite Sebring Plus.
 
Sounds like you gauge is very wrong should be almost mid way at warm idle and close to 3/4 at cruise , I think it'is supposed to be 10 lbs for every 1000 rpm above idle pressure roughly . Thats a heck of a viscosity is that pure synthetic ?
 
UHM I know that road, all uphill and prob the pickup went dry if you were a bit low. Center sump oil pan?
 
You might want to add an extra 1/2 quart to it next time. If it's low going up hill, and higher going down, it might be a suction side issue too. But - chances are if the oil pressure gets too low, the lifters will start clacking too. It might be a gage issue too.
 
Climbing hills put's a heavy load on the motor and it runs hotter. This heat in turn lowers the viscosity of the oil causing lower oil pressure. As you coast down the hill, cools the motor down and in turn cools the oil giving the higher pressure again.
 
FYI
About a month ago I towed our camper with my 360 truck, I seen the oil pressure go down to 40 psi on the interstate 3000 rpms, 5W-30, fresh cut crank, recondition rods, 180 deg f temp on the gauge, stock melling oil pump. Motor rebuilt 2000 miles ago.
I was not worried at all, when it starts cold it 70 psi plus.
Its just the physics involved, hard pull, with alot of weight 3500# camper and 1500# in the truck bed, is going to make heat, and when oil heats up it thins out.
 
25w60 is the strangest grade I've ever heard of. Where did you even find out about that? Everybody on the planet runs very conventional grades like 10w30 and so on and has ZERO problems.
 
RustyRatRod said:
25w60 is the strangest grade I've ever heard of. Where did you even find out about that? Everybody on the planet runs very conventional grades like 10w30 and so on and has ZERO problems.
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Back in the day you could get Castol in a 10w50 but it was almost double a 20w50. I loved that oil but most didn't because they didn't want to pay a buck seventy five a quart!

BTW, Torco makes a 20w60 full synthetic. It's designed for some European engine IIRC. I almost used it and then said screw it and closed up my clearances so I can run 5w30 or maybe even 0w20. It expensive. $23.00 per quart.
 
But who the **** needs 50 or 60 weight oil? NOBODY.

And if you think you do, you're a bigger idiot than I thought.


yellow rose said:
Back in the day you could get Castol in a 10w50 but it was almost double a 20w50. I loved that oil but most didn't because they didn't want to pay a buck seventy five a quart!

BTW, Torco makes a 20w60 full synthetic. It's designed for some European engine IIRC. I almost used it and then said screw it and closed up my clearances so I can run 5w30 or maybe even 0w20. It expensive. $23.00 per quart.
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80 wt oil used in aircraft engines
Think i got some time x 120 kicking around here somewhere. I dump it in the cockshutt when it needs.
Sae 40 is about the heaviest i would want to ever see in a car engine.
20w50 in air cooled bikes i guess is normal.
 
My friend had a 99 GMC suburban with 350,000 miles on it and 20w50 wt kept it alive till he was going to NC to pick up a boat. His girl friend was using it at the time and had the oil changed for him while she was out running around, put in 5w30 that was on the fill cap. He had to pull over in Beckly WV and it was banging real bad, had it towed to a garage and they told him this was the end of the road.
He called me wanting to know what to do and I told him to find some kendall nitro 70w, change the oil and get as close to home as you can. He found some 60w at napa and put that in and headed home, he mad it about 250 miles from beckly to north of new philly ohio and she gave it up, 30 miles from home. Yes viscosity has a lot to do with it when you need it.
 
Sure, maybe when you need it in an emergency, but other than that, it's a crutch for something W R O N G.
 
RustyRatRod said:
But who the **** needs 50 or 60 weight oil? NOBODY.

And if you think you do, you're a bigger idiot than I thought.
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Well let's see...when bearing clearances get up over .0029 or so with flimsy blocks and cranks, most everything running power adders, methanol fueled engines where the guy wants ring seal, as low viscosity oils and most synthetic base stocks don't deal rings very well, some European car makers call for it, and I'm there are others I'm just not thinking about.

Not everyone is looking for fuel mileage.
If you read close, you'll note I'm either going to use 5w30 or 0w20. The last time Castrol offered 10w50 in this country was 1982.

Oh yeah, most aluminum Rod engines and most aluminum block engines can use a 50.
 
It's the differences between an old motor designed to run 10w40 and a new motor designed to run 5w30 or 0w20 has a lot to do with machining tolerances
 
yellow rose said:
Well let's see...when bearing clearances get up over .0029 or so with flimsy blocks and cranks, most everything running power adders, methanol fueled engines where the guy wants ring seal, as low viscosity oils and most synthetic base stocks don't deal rings very well, some European car makers call for it, and I'm there are others I'm just not thinking about.

Not everyone is looking for fuel mileage.
If you read close, you'll note I'm either going to use 5w30 or 0w20. The last time Castrol offered 10w50 in this country was 1982.

Oh yeah, most aluminum Rod engines and most aluminum block engines can use a 50.
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Who was talkin about race stuff till now? Nobody.
 
RustyRatRod said:
Who was talkin about race stuff till now? Nobody.
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Is a 2017 BMW a race car? Is an engine with .0029 on the mains (about as tight as I go with a stock BB mopar) is getting close to needing a 50 if you put any load on it.

To say NOBODY needs a 50 unless they are stupid is wrong.
 
Maybe it's a little hotter in Mexico than in comfortable Ga, that where we are talking about isn't it
 
yellow rose said:
Is a 2017 BMW a race car? Is an engine with .0029 on the mains (about as tight as I go with a stock BB mopar) is getting close to needing a 50 if you put any load on it.

To say NOBODY needs a 50 unless they are stupid is wrong.
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Ok, I'll agree that far. But nobody driving an old Mopar street car needs it. And if they do "need" it, either they are misinformed, OR they have a wore out POS or some other malfunction.
 
Why not buy an oil pressure gauge and stop all of this guessing, unless it is not that important. Gauges are cheap and you can install a "T" fitting on the back of the block under the sending unit and have both. An idiot gauge where you hope you are guessing the correct pressure and a direct reading gauge, calibrated with actual pressure readings. Done. If you really need these weird high viscosity oils, You need to plan on a rebuild when you get home.
 
MoparLeo said:
Why not buy an oil pressure gauge and stop all of this guessing, unless it is not that important. Gauges are cheap and you can install a "T" fitting on the back of the block under the sending unit and have both. An idiot gauge where you hope you are guessing the correct pressure and a direct reading gauge, calibrated with actual pressure readings. Done. If you really need these weird high viscosity oils, You need to plan on a rebuild when you get home.
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Exactly my point. If you "need" high viscosity oil for good oil pressure, you got "other problems".
 
I run a 15 / 50 full synthetic but it's so thin it's like mineral oil and the 40 wieght seeps through the gaskets when it gets real hot out . now a 50 weight dino oil would be like running freaking engine honey but still a 25 / 65 is the weirdest combo I've ever heard of .
 
Id try a 10W40 on the way home, see what the mileage comes up to. 60W is tough on the pump and youll probably pick up a few MPG on the way home. 60W is what it is when hot and since you dont live in a freezing environment, you probably dont need the ultra thin 'start up' 0W. I believe the newer cars use the ultra low weights for start up emissions and can due to tighter manufacturing processes.
 
My '72 318 motor is old and I'm sure clearances have opened up some. The factory gauges were just refreshed/rebuilt by one of the most reputable classic gauge restorer's and I believe them to be accurate. It is a center sump pan but I made sure the oil level was at least to the full mark before the climb.

The high mileage Castrol 25W-60 is in stock and on the shelf in Mexican Autozones. Keep in mind, the Mexicans don't throw anything away, run their tires down to the cords, and run their cars until they die and can't be resurrected without a saintly miracle. In a desert climate like Baja California Sur (where the Baja 1000 is run) I believe there is a market for this grade of oil.

Part of the reason for my trip is to take home parts for the rebuild of a 340 core I purchased. This will be the last long-range (3000 mile) road trip for this 318 motor.

Anyone want to run/try/experiment with the 25W-60 Castrol high mileage oil can find it here:
Castrol GTX High Mileage SAE 25W-60 Motor Oil 6pk | eBay
 
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