The owners manual for the 1926 Stutz calls for the following engine oil:

Viscosity at 100 F warm weather 515 Saybolt cold weather 375 Saybolt

Viscosity at 212 F warm weather 63 Saybolt cold weather 57 Saybolt

I tried using conversion charts to figure the SAE oil weight but some tables are in SSU and some are in SSF thus requiring a multi-step conversion. Exactly what weight oils do these refer to? I know many of you want to be helpful, but please, no guesses. I am looking for a consistent (and correct) conversion method that works for all Saybolt numbers. Thanks for any help you can provide.

Steve

I dont know that it is possible. Even the later SAE numbers are somewhat arbitrary. Dykes manual (1931) states it this way. @100 deg. Light oil = 200-260 seconds, Medium = 260-400, Heavy = 400-800, Extra heavy = 800-1300 seconds. At 212 deg. Light = 43-47 seconds, Med.= 47-55, Heavy= 55-70, extra heavy= 70-100

If anyone has the answer to your question these people will.

http://www.penrite.us/nextpage.php?navlink=

Penrite Oil Company specialises in making lubricants for antique cars and motorcycles 1895 and newer. They should be able to interpret those numbers for you.

If you want to cut right to the chase here are their recommendations for Stutz 1930-36 models. Sorry no specific listing for 1926.

http://www.penrite.co.uk/nextpage.php?na...;x=275&y=18

Rusty,

Thank you for the lead. I have sent them an email and we will see what they have to say. Although I started this by quoting the Stutz Handbook, I am not asking just about Stutz. I have no problem finding and using the correct oil for it. I am looking for a consistent (and correct) conversion method that works for all Saybolt numbers. Does such an algorithm exist?

Steve

I know what you are driving at but don't know the answer. You would need a chemist who is up on the history of oil technology and familiar with testing methods that are now 80 years old or older.

By the way I wouldn't put much stock in Penrite's recommendations. I checked their web site for my 1951 DeSoto. They recommended 90 gear oil for the transmission. The factory recommends 10wt motor oil. They omit the fluid drive unit entirely. This information is applicable to Chrysler Corporation cars from 1939 to 1954 and is available in any Chrysler manual from the era. So I take it their automated recommendations are of a blanket nature and not well researched.

I received a very nice reply to my question about oil viscosity measurement from Andrew Poole of the Penrite Oil Company. I have pasted it below and have attached the accompanying chart.

Comparison of viscosity classifications


Firstly, my apologies for not answering your question more quickly.

I have attached for you a comparison chart which shows approximate equivalents of the two major measures of viscosity (Kinematic and Saybolt) and a number of viscosity classifications systems. Please note that they are only approximate but should serve their purpose for you.

In looking at the Stutz recommendation I would suggest you look only at the viscosity at 212ºF that being the equivalent temperature to that used to specify the SAE grades (both engine and gear).

You will note that the temperature in the chart for Saybolt viscosity is 210ºF not 212ºF but for the purposes of this exercise the variation of 2ºF will not make a difference.

To read off the equivalent SAE viscosity take a horizontal line from the SUS at 210ºF through the SAE grades from which you will see that in summer Stutz are recommending what is now a heavy SAE30 and for winter what is now a borderline SAE20/SAE30.

Similarly if you had a gear oil recommendation of, say, 160 SUS at 210/212ºF you would take your horizontal line across to the SAE Gear Oil column which would indicate an SAE140 should be used.

Ignore the other two viscosity classifications - AGMA is for industrial gear oils, ISO for other industrial oils and have no application to your type of use.

Note also that whilst Kinematic Viscosity is a modern universal viscosity measurement, Saybolt is essentially American. A car of the same age as your Stutz but made in the UK might well quote a Redwood viscosity whilst if it came from Europe it might be an Engler viscosity. The latter two types of viscosity are rarely referred to today and their conversion is much more convoluted.

Trust the above is of use and interest to you.


In relation to your question on the worm drive oil, the comment in the Stutz literature is correct for its time but not necessarily now.

Penrite Transoils are straight mineral oils, that is they contain no additives. Refining techniques have improved markedly since 1926 and one of the results is that today's oils have very low sulphur content, and that which is present is chemically inactive, so that it does not attack yellow metals. Transoil is therefore absolutely safe to use in your worm drive.

Where care is needed is where an EP additive containing oil is contemplated for use in a worm drive (such as a modern hypoid differential oil). Some of these will attack the bronze although others may not, it depends on the chemistry.

However, it is only with later worm drives where the loading on the gears is sufficiently high to need an EP additive containing oil, eg. Peugeot continued using worm drives way past the time most other manufacturers had turned to hypoid drives, and these do require an EP additive containing oil.

Again, trust this is of use and interest to you.

Andrew Poole
Penrite Oil Company

Hi Steve !

Is it really YOU ? Hope you and yours are doing well - been a long time. I still show up occasionaly at So. Calif. Reg. meets - hope to see you there !

Regarding your question - may I reduce some great responses you've received, to a simple sentence ? YOU CAN NOT GO WRONG USING MODERN OILS !

I know you are technically competent, so I presume you "dropped the oil pan" on the engine (to clean out sludge and other "muck" you dont want getting pumped thru the engine) and drained and flushed (presumably with cleaning solvent, but kerosene is fine (but I know you know all this stuff..!)

Starting out fresh, you can, safely and with confidence, use ANY "off the shelf" 10-30 or 20W-40 multi grade oil on which the container it says something to the effect "meets engine maker's specs". Same goes for your differential and transmission gear case. Not knowing your transmission, I presume it does not have modern synchronizers, so I would stick with a heavier gear oil to make shifting (gear oil "drag") easier - a ordinary 140 W modern gear oil would work just fine.

The mischief caused by oil company advertising people is still upon us. There is NO SUCH THING AS "DETERGENT" oil ! That is an ADVERTISING phrase ! Modern oils cant "wash" anything from your engine. All they do is keep small carbon molecules in SUSPENSION, so they can be drained and filtered away (prevents them from "linking up" and causing sludge.

Modern EP gear oils will protect your transmission and rear axle gears FAR better then anything available pre-war.

Good luck - and remember what I used to say when I was active in your Region ( "if you cant drive em..junk em" )

Best Regards

Pete <img src="http://forums.aaca.org/images/graemlins/wink.gif" alt="" />

Yes, it's me. Give me a call sometime. I'm in the directory.

The latest oil formulas have cut way back on certain additives. The result is greatly increased wear on engines with flat tappet cams.

They cut back on the additives because if your engine burns oil, the additives will poison the catalytic converter. And modern engines use roller tappets so who cares about flat tappet cams.

This is especially critical when breaking in a new cam or new engine.

I suppose old flathead engines with low spring pressure won't be hurt but a lot of more modern engines are suffering.

The solution is to use diesel motor oil which has a heavy duty additive package. Or buy an oil supplement $$$$.

The Stutz uses a spring pressure of 90 pounds. How does this compare with modern engines?

Steve