Synthetic oil

We have beat this oil thing to death for years. It seems the conclusion was almost any oil that feels slippery between your fingers worked in these old engines if changed frequently. I used Castrol 20/50 in all of my engines gas and diesel for over 35 years. I put a brand new WW11 engine in my 39 33 years ago, drive it harder than most and put over 120,000 miles on it. At 85,000 while changing the oil I felt the pick up screen move and pushed on it a few times and the tube and screen dropped into the pan. I removed the pan a brazed the tube back on the boss. The pan and underside of the engine was perfectly clean with not a spec of sludge. There was an area of about 3"s in diameter at the lowest spot of the pan next to the drain plug. This was hard and I suspect fine casting sand from the new engine. I scraped it out. I think I can find a picture of the bottom end I took. I have several expensive modern diesels and due to warrantee I used the recommended shell oil in them until I discovered the properties of Valvoline Cummins Blue diesel oil. This oil had all of the additives which I believe along with the experts can extend engine life. Seeing this I started using it in my old Fords. Now we will hear from some who say diesel oil is not good for gas engines but I don't buy it. The Castrol 20/50 up until a few years ago was diesel oil. I used the 20/50 in the new 39 engine from the original start up. This engine burnt some oil and got black in a few miles for 15 or 20,000 when it ran up near 200 degrees. After getting it cooled to the 170 range it stopped burning oil and the oil gets to a dark yellow. At 120,000 miles I never add any between changes. If your happy with and think your oil is the greatest continue to use it. If your looking to make a change read the makeup of the Valvoline Cummins Blue. G.M.
 

Attachments

  • 39 crankshaft-1.jpg
    39 crankshaft-1.jpg
    64.9 KB · Views: 84
  • 39 Crankshaft-2.jpg
    39 Crankshaft-2.jpg
    65.1 KB · Views: 75
  • TDR57_Oil.pdf
    TDR57_Oil.pdf
    166.6 KB · Views: 34
Last edited:
This is great info and what I'm looking for. Long term use of something that works. I'm new to the flathead V8, and have read, and read, and realize the subject has been kicked to death, hence the reason I am sort of confused as what works, and what don't. I've heard bad, and good about using 20/50 diesel oil, but good to hear from a long term user of it. Thanks for your info.

My biggest problem is I have a tad bit of OCD, and a chronic gauge watcher. Always have been. I just like to know what's going on under the hood, even with my daily driver Dodge Ram diesel. I monitor all gauges all the time. Not paranoid, just me. The issue I have that I have to learn not to let bother me is low oil pressure on the flathead. I know it's characteristics of these motors from what I hear. But damn, I am trying to fight my OCD with that, lol.

G.M. said:
We have beat this oil thing to death for years. It seems the conclusion was almost any oil that feels slippery between your fingers worked in these old engines if changed frequently. I used Castrol 20/50 in all of my engines gas and diesel for over 35 years. I put a brand new WW11 engine in my 39 33 years ago, drive it harder than most and put over 120,000 miles on it. At 85,000 while changing the oil I felt the pick up screen move and pushed on it a few times and the tube and screen dropped into the pan. I removed the pan a brazed the tube back on the boss. The pan and underside of the engine was perfectly clean with not a spec of sludge. There was an area of about 3"s in diameter at the lowest spot of the pan next to the drain plug. This was hard and I suspect fine casting sand from the new engine. I scraped it out. I think I can find a picture of the bottom end I took. I have several expensive modern diesels and due to warrantee I used the recommended shell oil in them until I discovered the properties of Valvoline Cummins Blue diesel oil. This oil had all of the additives which I believe along with the experts can extend engine life. Seeing this I started using it in my old Fords. Now we will hear from some who say diesel oil is not good for gas engines but I don't buy it. The Castrol 20/50 up until a few years ago was diesel oil. I used the 20/50 in the new 39 engine from the original start up. This engine burnt some oil and got black in a few miles for 15 or 20,000 when it ran up near 200 degrees. After getting it cooled to the 170 range it stopped burning oil and the oil gets to a dark yellow. At 120,000 miles I never add any between changes. If your happy with and think your oil is the greatest continue to use it. If your looking to make a change read the makeup of the Valvoline Cummins Blue. G.M.
Click to expand...
 
On my post above it did not list the oil make up, I changed the attachment which you have to click on so it includes the oil make up. I like the molly and zink additives. Low oil pressure on any engine is not good. Low oil pressure in a flathead is from a problem not a natural event. They should have at least 8 to 10 idle and 30 plus at driving speed hot. Oil also cools the engine so more oil flow changes the oil faster between the moving parts. The biggest problem is the oil bypass valve and in some cases the oil pump gears or clearance between the bottom of the gears and bottom plate. On later model pumps it can be the bypass valve built into the pump. The guessing and part changing approach don't suite me. I want to find, see and fix the problem. I have stated many times on this site that I wouldn't put ANY pump new or used in one of these engines without testing it and seeing the results. The pump is to the engine as the heart is to the body. Several days ago I posted a picture and description of a simple way to test an oil pump so you know you won't need a pump transfer or replacement right away not to mention work, damage or premature wear on bearings and other parts with hardly any oil circulating. The engine can be spun on 12 volts with the plugs out, intake manifold off and a mechanical oil pressure gauge in the car or sitting on the floor. This will give you the oil pressure you can expect at driving speeds. If it is the front bypass valve you can shim the spring to the pressure you want. Any proper working oil pump will deliver over 60lbs of pressure and the bypass can be adjusted on the pump and or front valley valve to 45 or 50 lbs. If you have a pump and valley valve one must be set for a high spring pressure so the other one controls the pressure you want. G.M.
 
So the only way to solve this problem is to find someone that can put 120,000 miles on his Flathead wit 5/20 Synthetic oil, and compare them. I read an NASCAR artice a while back where the 5 wt oil ran cooler. The engines of today use this oil for a reason, Its better for the engine. The same reason we use better ignition systems and Fuel systems and we don't fly around in Bi-Planes any more. One thing I do know for a fact is the relief valve in an oil pump generates a tremendous amt of heat and with 20/50 oil it's doing just that.
 
With all this said, what is the zinc % recommended for an oil in these motors? An oil I'm looking at is Castrol GTX 20W-50 which has %w .09 zinc.
 
Don't cut me off at the knees but I was told that it was bad to run 5W oil on older engines (not specifically flatheads) because the tolerances and materials on the old engines were not designed for it. Don't remember where I read or heard it but it kind of logically makes sense to me. My opinion is if the oil is being changed every 1000 miles why spend the money on synthetic but if you are going 3K on a change then I probably would run synthetic.
 
Ol' Ron said:
So the only way to solve this problem is to find someone that can put 120,000 miles on his Flathead wit 5/20 Synthetic oil, and compare them. I read an NASCAR artice a while back where the 5 wt oil ran cooler. The engines of today use this oil for a reason, Its better for the engine. The same reason we use better ignition systems and Fuel systems and we don't fly around in Bi-Planes any more. One thing I do know for a fact is the relief valve in an oil pump generates a tremendous amt of heat and with 20/50 oil it's doing just that.
Click to expand...

I can only tell you what happened on my engine, I don't deal with "what if's". The clearances and tolerances on todays engines aren't like the old Fords. The only reason I could see for a bypass valve in an pump causing higher heat would be it reduces the flow of oil through the engine, keeping the oil confined in the hot areas for a longer period of time. G.M.
 
The OEM flathead valve springs have lower pressure than most all overhead valve engines so the need for more ZDDP didn't really come about until the later OHV engines started to have problems with cam & tappet wear. Later in the 50s & 60s they were making the engine with higher compression & horse power and made it even more important to use anti scuffing additives. You could probably run a flathead on castor oil if you had to but it would make you sick with the smell.
 
When rebuilding these engines we have the opertunity to take advantage os such things as Full floe oil filters and control the bearing clearances among other things such as adding dual exhaust, electronic ignition systems and other dudads. so taking advantage o fSynthetic oil as a method of improving the longivity of your investment ain't a bad idea. 5K between oil changes makes it cheep oil.
 
G.M. said:
I can only tell you what happened on my engine, I don't deal with "what if's". The clearances and tolerances on todays engines aren't like the old Fords. The only reason I could see for a bypass valve in an pump causing higher heat would be it reduces the flow of oil through the engine, keeping the oil confined in the hot areas for a longer period of time. G.M.
Click to expand...

Relief valves do cause heat from friction at the molecular level. I don't know how much that would affect a 50-80psi system but when I worked on aircraft hyd systems with 3000psi, a faulty relief valve would overheat the system very quickly.

Lonnie
 
Last edited:
rotorwrench said:
Carbureted engines always have more fuel traces in the oil just due to their inefficiency. If the power valve blows out or the bowl starts to leak, (and they always eventually do) then even more fuel ends up passed the rings or valve guides. It's just the nature of the beast.

In large aircraft, they used to have a dilution system that added fuel to the oil in the pickup hopper part of the oil tank so the engine would start in cold weather. This made for some short life oil but the oil was changed every 25-hours so it was no big deal.
Click to expand...

I understood the fuel evaporated when the oil and engine heated up.
 
Tudorp said:
My biggest problem is I have a tad bit of OCD, and a chronic gauge watcher. Always have been. I just like to know what's going on under the hood, even with my daily driver Dodge Ram diesel. I monitor all gauges all the time. Not paranoid, just me. The issue I have that I have to learn not to let bother me is low oil pressure on the flathead. I know it's characteristics of these motors from what I hear. But damn, I am trying to fight my OCD with that, lol.
Click to expand...

Ah, a man after my own heart. :)
I watch the gauges too and, even though I believe that any minimal flow of oil is sufficient to get it where it needs to be, I still like to see the gauge read somewhere above the bottom. So, for engine starting temperatures above 60°F I use S.A.E. 40. It produces 60 p.s.i when first started and only drops to 30 p.s.i. when fully heated up. Any idle speed fast enough to keep the generator charging keeps the hot oil pressure at 20 p.s.i.

So, bottom line: If you like to watch the oil pressure gauge, experiment with different weight oils (I like straight over multi-vis*) until your gauge reads what you want then stick with it. (Of course, this is all based on having an accurate oil pressure gauge which may mean mechanical as per your previous thread: http://www.fordbarn.com/forum/showthread.php?t=134925)

*Here's a great discussion comparing straight vs. multi-vis oil and conventional vs. synthetic I learned a lot from: http://www.upmpg.com/tech_articles/motoroil_viscosity/
 
Last edited:
Tudorp said:
With all this said, what is the zinc % recommended for an oil in these motors? An oil I'm looking at is Castrol GTX 20W-50 which has %w .09 zinc.
Click to expand...

I've studied this "Zinc Question" at length over the years. The sellers of ZDDPlus had me sold on its necessity for the non-roller cam/lifters and I added their expensive product for a few years until I read a study that tested the effects of zinc on the stock flathead cam/lifters and proved that, because of the low valve spring pressure, no zinc needs to be added to any modern oils. They all have enough for the stock flathead valve spring pressures without adding any. (Wish I had saved that study. It was very good with photos of the cam/lifter wear surfaces and everything.)
 
G.M. said:
Now we will hear from some who say diesel oil is not good for gas engines but I don't buy it. G.M.
Click to expand...

Here it is::)

Why not use oil rated for spark ignition, which flatheads are, instead of oil formulated for compression ignition, which diesels are? Doesn't make sense to me. Gasoline and diesel oils have different additive packages because the contaminants in the crankcase are different. With a gasoline engine you get a lot of moisture and tar and with a diesel the oil becomes acidic and will collect more carbon. It's always best to use an oil specially formulated to the type of engine for optimal life.

You will see things like "API SG or CJ" on the oil container, that means:

API = American Petroleum Industry
SG = Spark ignition (for gasoline engines), grade "G"
CJ = Compression ignition (for diesel engines), grade "J"

The second letter is the grade designator, in alphabetical order, and later = better.

I know I've said all of this before but I will say it again every time someone recommends that oil formulated for diesel engines be used in our flatheads.:cool:

But, having said all of that, I don't actually believe any particular oil is critical and have done just what I suggested two posts up - picked the viscosity that created the pressure I wanted to see on my gauge and that was it. :rolleyes: I get the cheap NAPA brand conventional high detergent oil.
 
Last edited:
Old Henry said:
Here it is::)

Why not use oil rated for spark ignition, which flatheads are, instead of oil formulated for compression ignition, which diesels are? Doesn't make sense to me. Gasoline and diesel oils have different additive packages because the contaminants in the crankcase are different. With a gasoline engine you get a lot of moisture and tar and with a diesel the oil becomes acidic and will collect more carbon. It's always best to use an oil specially formulated to the type of engine for optimal life.

You will see things like "API SG or CJ" on the oil container, that means:

API = American Petroleum Industry
SG = Spark ignition (for gasoline engines), grade "G"
CJ = Compression ignition (for diesel engines), grade "J"

The second letter is the grade designator, in alphabetical order, and later = better.

I know I've said all of this before but I will say it again every time someone recommends that oil formulated for diesel engines be used in our flatheads.:cool:

But, having said all of that, I don't actually believe any particular oil is critical and have done just what I suggested two posts up - picked the viscosity that created the pressure I wanted to see on my gauge and that was it. :rolleyes: I get the cheap NAPA brand conventional high detergent oil.
Click to expand...

Cheapest isn't always the best. You should have learned that by now on almost every repair you made on your car. Then when it fails you have more trouble finding the problem than most people, I guess because you know everything. G.M.
 
I really appreciate all the comments. Although it seems that it is still a well discussed issue. I have read, and still reading the links on oil science. It really is a science. Good points on all sides. A couple points also that don't make sense to me, but food for thought none the less. I think what it boils down to is what you are best comfortable with in your motor (regardless if the motor appreciates the same comfort). Bottom line is, I'm still confused.. lol.. I am not a mechanic by trade, but have built cars, and or motors and pretty good skills with that, but the science of motor oil has always eluded me really. I just always ran what I felt is best with good results so far over the years. Now with being new to the Ford flathead V8, started my inquiry all over again. My car has been running and sounding fine with next to no pressure on the gauge. However I haven't run it much since I only purchased it just before I stored it for the winter. Right or wrong, I like to see the needle actually do something. Sorry, it's just my OCD. That way, I at least know the oil pump is actually earning it's keep. This is what I have decided to do. I picked up this oil, and will add this zinc additive for additional security. We'll see how this pans out.

castol_zps95f89f06.jpg
 
Go ahead and use the zinc additive if it makes you feel good. It absolutely is not needed. Too much zinc can also cause problems as I'm sure you have read.
 
You must log in or register to reply here.
Back
Top