600w gear oil vs AMSOIL PRODUCTS

[Marco Tahtaras]

Originally Posted by H. L. Chauvin

Hi Josh,

According to AMSOIL written specifications, AMSOIL ISO 460's Viscosity Index is 139 as opposed to 90 - 95 for various Steam Engine Oils like the 680 Series, MOPAR etc.; hence, Amsoil is less affected by differences in higher & lower temperature changes.

The Viscosity cSt at 100 degrees C is C = 42.8 compared to Steam Engine Oils at C = 36.4 - 39.2; & the cSt viscosity at 40 degrees C is, C = 484.6 as compared to C = 646 - 680 for Steam Engine Oils.

He's correct here but C=484.6 Compares to SAE140 at best where (original) C=680 equates more closely to SAE250 which Ford changed to in 1932 except for sub-freezing temps. BIG difference at operating temps!

I am familiar with 600W Super Cylinder Oil, used in old Fords. It was an ISO 460 non-EP gear lube. AMSOIL ISO460 Gear and Bearing oil is recommended as a replacement for it when used in these cars. Its product code is RCO and is available in 5 gallon and larger quantities. See http://www.amsoil.com/storefront/rc_series.aspx

Byron Selbrede
Technical Services

Now he shifted gears and equates the original to ISO 460, probably because Mobil changed their classification for "600w" in recent years from ISO 680 to ISO 460. The viscosity difference is significant.

With that said, the difference in viscosity adds little IF ANY value in lubricating qualities. Where it does make a difference is in seepage through unsealed passages to the outside which are many among the steering and transmission. Additionally, some folks find the higher viscosity better for shifting. Personally you could put in the viscosity equivalent to water and I'd adapt very quickly and both upshift and downshift with relative ease but that's me.

There ARE benefits to the higher viscosity lubricant originally employed by Ford but there is so much misinformation out there it becomes difficult to compare apples with apples.

[Art Bjornestad]

Any type of hypoid oil...any modern oil, is designed to leave a slight film on gear faces. These modern cut faces are under very severe wiping action and will get destroyed if a non hypoid oil is used. That is why they are labeled EP......extreme pressure.

The reason why the above is true is that 600 type (non hypoid) oils have a heavy cling action, perfect for straight cut gears but bad for modern gear cuts as the oil is sticking to the gear faces, just where it shouldn't be, and can cause tooth breakage and case hardening corrosion.

If you turn an A tranny when it is dry and on the bench you will hear the gears banging as they make face contact. Modern trannys are silent because the gears meet in a wiping action.

[Tom Wesenberg]

"perfect for straight cut gears but bad for modern gear cuts as the oil is sticking to the gear faces, just where it shouldn't be, and can cause tooth breakage and case hardening corrosion."

I would think oil on the gear faces would be great no matter straight or hypoid?

[H. L. Chauvin]

There are tons & tons of information on Gear Oils on the Internet if one is sincerely interested in reading reports from independent laboratories.

An important interesting concern one may want to consider only "if" living in extreme colder areas is that experienced by the gentleman in Reply no. 2 above, i.e., reporting one transmission lubricant at -35 degrees F was a failure; however, reporting an experience of switching to a transmission lubricant like AMSOIL that has a high Viscosity Index, (the higher the better), whereby no problems occured.


In the mentioning reply no. 19 above, the ANSOIL gentleman's reply is only the one in blue, responding to several very detailed questions I had sent him concerning straight cut gears. -- I had extracted & wrote the AMSOIL viscosities from the AMSOIL written specifications comparing same to the 680's etc just in case anyone was interested in same..


One can find that the gear box lubricant temperature at rest & the gear box lubricant temperature when in operation, are both naturally affected by the local ambient temperature; however, even though engine oil weights are specified differently for summer & winter, the same type of gear oil was & still is specified for both summer & winter; hence, viscosity indices will make a difference.

It would not be alarming to find that the former 600W used by Ford had a high viscosity index, otherwise it would not have functioned so well with varying ambient temperatures. Viscometers to determine viscosity of petroleum products were in use by major oil companies well prior to the Model A.


Also when trying to compare apples to apples, ISO is used a lot for industrial purposes whereas SAE is preferred for automotive purposes; however, a gear lubricant with a rating of SAE 140 can be equal to an ISO gear lubricant of anything between ISO 460 "and also" ISO 680 because the ISO Kinematic viscosity depends on the grades of centistokes all tested in the metric system accordance with ASTM D-445 established as early as 1937 when former 600W was still around & in use.

I just hope Josh has an answer to his initial question.

[Special Coupe Frank]

Originally Posted by Tom Wesenberg

"perfect for straight cut gears but bad for modern gear cuts as the oil is sticking to the gear faces, just where it shouldn't be, and can cause tooth breakage and case hardening corrosion."

I would think oil on the gear faces would be great no matter straight or hypoid?

The "sticky" of the 600-weight, inhibits the sliding / wiping action of the hypoid gears. I had not heard of breakage being a consequence, but definitely accelerated wear when non EP lubes are used with Hypoid gears.


As for straight-cut (spur) gears "banging" as each each pair of teeth make contact, if you go to a tractor show where there are steam tractors or very large early gasoline tractors where the drive gears are all exposed, you'll probably hear the spur-gears clattering as the machine rolls by.

SC Frank