Castrol D140 is better then any 600w oil from the 1920-30 's.
The problem is not if the oil is better, but if it is the correct type of oil for the application. You do not use watch oil in your engine.
Gear oil for modern gears is not the correct type oil for the straight cut gears used in the A.
Here is what others have researched so you can have the correct type modern oil for the A.
Re: Mobile 636 gear oil
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Posted by Marco Tahtaras from c-24-4-43-195.hsd1.ca.comcast.net (24.4.43.195) on Saturday, August 09, 2008 at 9:38AM :
In Reply to: Mobile 636 gear oil posted by Bob from ? (64.237.121.113) on Friday, August 08, 2008 at 10:35PM :
Mobil:
Mobilgear 636 (Which has been replaced with MOBILGEAR 600xp 680 11/27/2011)
BP:
Energol GR-XP 680
Castrol:
Castrol Alpha LS680
Shell:
Omala 680
Texaco:
Meropa 680
Here is some more info
Re: 600W Thickness -- One (1) Answer
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Posted by H. L. Chauvin on Nov. 26, 2011 at 16:34:03
In Reply to: Re: 600W Thickness, Transmission Gear Grinding
posted by louis on Nov. 25, 2011 at 17:19:35
Hi Louis,
Your former question made sense when someone new to this Forum reads "all" of the many "different" former 600W discussions in the attached archives.
It appears most "salespersons", (parts suppliers & oil compaies), offer the 1930's 600W substitute, but as Marco noted in the archives in the late 1990's, they are "not" all the same.
Many articles appear on experiences of switching to thicker transmission oil; thus eliminating driver's not experiencing grinding of transmission gears.
Gear oil thickness, (resistance to flow), is measured by several methods.
Kinematic Viscosity per ASTM D445 is one standard method indicating the milimeters squared divided by time in seconds at 40 degrees C, or 104 degrees F, which is closest to trasmission gear oil viscosity after attaining operating temperature.
For example, per ASTM 445, water has low viscosity, honey has high viscosity.
The recommended BP Energol 680, Shell Omala 680, Mobile Extra Helca Super Cylider Oil 680, have ASTM 445 measured viscosities, (40 C), of a high 680; Texaco Mepora 680 indicates a thinner 646; however, Valvoline 85/140W drops down to 395, & Castrol 85/140W is thiner at 369.
One of the "most" scientific test conducted on Ford's 1930 recommended 600W appears to be a gentleman who wrote that he had an old sealed can of
Ford's recommended 600W.
After trying many gear oil substitutes, his highly scientific lab test indicated that the 600W was extremely thick, almost like melted tar, & equal to the above mentioned 680 viscosities.
His test, he dipped his finger in each & watched it flow!
It appears if one uses recommended gear oil with a viscosity of 680, & gears continue to grind, begin looking somewhere else.
Hope this helps 1930's future 600W research.
