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resurrection20 
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Joined: 14 Nov 2023
Location: Oregon
Points: 81
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 Topic: Straight 40 weight in a Model 'B'
Posted: 19 hours 11 minutes ago at 11:49am |
Thought I'd see if I can become the pariah of the day on here. ;)
I've had recommended to me recently by some other B, C, and CA owners to move up to a straight 40 weight if your engine is a little clanky, like mine is. Right now I have straight 30 weight in it. Oil pressure starts out great in the middle of the gauge, but eventually peters down to the "low" side after it's fully warmed up and hovers right on the line between "low" and "normal." It is an aftermarket gauge. My old one always read higher and had numbers, but something blew out inside it and oil filled up the inside of the gauge, so I got a new one from Steven's Lake Parts and it's always read lower, which makes me think it's one of those automobile ones that's meant for higher PSI (30+) cars that just has an "Allis-Chalmers" plate stuck in it for looks.
Regardless of whether I have a dud of a gauge, is it crazy to use Straight 40W in the shoulder seasons and summer when it's above 60 degrees F? Want to add that part that I understand winter multigrade oils and how much damage you can do using a straight weight oil below 32F, lol.
Alright! Commence keyboard flogging!
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Lars(wi)
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Joined: 14 Sep 2009
Location: Permian Basin
Points: 7843
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Posted: 17 hours 35 minutes ago at 1:25pm |
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No flogging from me, we ran straight 30w on the farm well after multi-grades were on the market.
If I went back farming, I would use straight 30w. We would change to multi-grade only after fall tillage was done, switch back in the spring before heading back into field work.
I have heard all the song and dance on how multi-grades a far better than decades ago, yes that’s true but, 30w engine oil is also far better than decades ago.
Edited by Lars(wi) - 17 hours 34 minutes ago at 1:26pm
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I tried to follow the science, but it was not there. I then followed the money, and that’s where I found the science.
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Allis dave
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Joined: 10 May 2012
Location: Northern IN
Points: 2992
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Posted: 16 hours 33 minutes ago at 2:27pm |
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I would consider 15w-40. I've known people running this weight in trucks that has oil consumption issues.
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DrAllis
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Joined: 12 Sep 2009
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Posted: 16 hours 30 minutes ago at 2:30pm |
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I'm not a B-C-CA kind of guy. I do know the connecting rod bearings are basically splashed lubed by the camshaft having a small orifice hole that lines up with the connecting rod bearing oil hole when they are at their closest point in rotation. You don't have a clue how many psi of oil pressure you have. 10-12 psi on one of those engines is adequate. 40 wt really doesn't lube as well as 20 weight does. Try and squirt 40 wt into the rod bearing oil hole. Get a gauge that isn't over 40 psi and see what you actually have. If it is a bad oil burner?? then maybe you could convince me to try 40 weight.
Edited by DrAllis - 16 hours 19 minutes ago at 2:41pm
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steve(ill)
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Joined: 11 Sep 2009
Location: illinois
Points: 86240
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Posted: 14 hours 56 minutes ago at 4:04pm |
Dr. is right.. this is a BYPASS SYSTEM.. 15% of the oil goes to the gauge, thru the filter and dumps back to sump.... The PRESSURE reading is due to the filter RESTRICTION... 85% of the PUMP OIL goes down thru the hollow cam shaft and thru ports to the main bearings, and thru orifices that spray the oil out of the cam toward the pistons / rods.
15 psi is NORMAL at high idle if the engine is in good shape and filter is good.. Pressure with a NEW filter might be a couple psi low untill the filter becomes soaked, and gets some BACK PRESSURE.... The filter and the 1/4 inch tube inside it are what causes the BACK PRESSURE on the gauge.... thinner weight oil could actually be pumped thru the orifices easiler and get you BETTER FLOW to the bearings and spray at the piston wrist pins..
Heavier oil will cause more back pressure in the filter and make the PSI reading go up.. It should also cause higher viscosity in the 85% of the oil going to the engine bearings / pistons... That might not get you MORE OIL, due to the THICKER VISCOSITY....
I would prefer a 10w- 40 of 15w- 40 oil if you think the 30wt is too thin.
I have seen more that one B engine that runs fine with 10 psi at high idle and 5 psi a low idle..... when you loose pressure on a B-C engine, its normally due to oil pump wear on the end covers... Too much thrust clearance and your loosing efficiency.
Edited by steve(ill) - 14 hours 48 minutes ago at 4:12pm
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Like them all, but love the "B"s.
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Les Kerf
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Joined: 08 May 2020
Location: Idaho
Points: 1112
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Posted: 13 hours 46 minutes ago at 5:14pm |
If I were planning to run one of these engines hard for long periods of time in 80+ degree weather doing something silly like plowing for 8 hours straight then I would probably run straight 40 Wt HD diesel oil. For the light duty putt-putting for which I actually use my Model C tractor I use only 10W-30 in the summer and 5W-30 in the winter. My engine sees lots of short runs and I want that oil to get circulating as soon as possible.
As mentioned above, these engines use a bypass-type oil filter. If you want to see higher oil pressure, don't change the filter. Did you know that filters actually do a better job of filtering after they start to get a bit dirty? As long as the filter continues to get warm you know that oil is still flowing through it and it is doing its job.
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steve(ill)
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Joined: 11 Sep 2009
Location: illinois
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Posted: 13 hours 31 minutes ago at 5:29pm |
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Correct.. An OLD or PARTIALY PLUGGED filter will restrict the 15% of oil dumped back to sump.. Pressure on the gauge will go up and more of the oil will go with the 85% that goes to engine Lube..
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Like them all, but love the "B"s.
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PaulB
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Joined: 12 Sep 2009
Location: Rocky Ridge Md
Points: 4967
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Posted: 12 hours 17 minutes ago at 6:43pm |
The CA is my favorite Allis Chalmers tractor. Take everyones advise for what you paid for it. It's your tractor, do whatever you feel is right. To properly understand motor oil viscosity labeling, Be aware the _ _W number it what it will flow like when it's cold and the other number it what it flows like when it's hot. Soooo with a straight 40 weight oil you get the cold and hot properties that a 40 weight oil specifies. At cold temperatures 40 weight will flow very sluggish and since about 90% of engine wear is from start up until it reaches operating temperature. Do you want to add to an already worn out engine? Granted a 40 weight oil will help with a rattling lower end, However the best thing would be drop the oil pan and take out a couple of shims from the rod bearings. Short of that try a 10W40 or 15W40. I personally use 15W40 in everything I have, makes it simple, 1 oil for everything.
Edited by PaulB - 12 hours 15 minutes ago at 6:45pm
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If it was fun to pull in LOW gear, I could have a John Deere.
Real pullers don't have speed limits.
If you can't make it GO... make it SHINY
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resurrection20
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Joined: 14 Nov 2023
Location: Oregon
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Posted: 11 hours 28 minutes ago at 7:32pm |
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My takeaway is that at best it's a waste of time and at worst it will cause unnecessary wear.
My tractor doesn't use any oil. I don't run it all that much, to be honest. Maybe 5-10 hours a year.
Thanks for your responses everyone. Now I'm wondering what straight 40 wt was designed for.
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Les Kerf
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Joined: 08 May 2020
Location: Idaho
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Posted: 10 hours 53 minutes ago at 8:07pm |
 resurrection20 wrote:
... Now I'm wondering what straight 40 wt was designed for. |
It's for extreme conditions such as "planning to run one of these engines hard for long periods of time in 80+ degree weather doing something silly like plowing for 8 hours straight". 
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