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Hello everyone,

I am new to this forum and the new owner of a 41 Buick Sedanette. I have a few questions I'd like to ask and forgive me if they sound like a novice question, but I am a novice when it comes to this car. I do own another newer classic (not as old) corvette and was a mechanic for g.m. for twenty five years but never on a car this old. There's not much I can't handle on this car mechanicly but the issues I have relate to all the fluids. I have the 41 GM shop manual, but all the fluids listed are by GM 's consumer names and part # and don't list weight or viscosity. Could anyone tell me the correct fluids for:

Rear Axle- is it still 90 weight gear oil?

3Speed Manual Trans. fluid

Brake Fluid DOT #

Engine oil- I plan on using straight 20weight in straight 8 w/ dual carbs.

I know this sounds stupid and I feel stupid asking for such a basic issue, but all the manual says is use GM or Buick " Super Dupper "or some other long discontinued type of name for their fluid. Please don't laugh too hard over this question, but I feel in love with the car the day I saw it and I don't want to make any mistakes on such a beautiful car. I'll probably have a ton of other questions as I get more into this car, but for now the basics are my main concern.

Thank's in advance to anyone who can stop laughing long enough to answer.

All the best



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Welcome to the AACA Discussion Forum. I would also agree that you will find plenty of help in the Pre-War Buick Forum if you scroll down there.


Based on my experience with a 1937 Buick, I would recommend that the best option for the Transmission and the Rear End would be the following: https://www.oreillyauto.com/shop/b/chemicals---fluids-16461/maintenance-chemicals-16867/grease---lube-16582/gear-oil---additives-16905/gear-oil---140w-20063/587d6374459f


Engine Oil recommendations will likely be all over the map from different forum members. Almost any modern oil you choose will be better than what was available in 1941. Diesel oils typically have higher ZDDP levels which are a good idea. There are also a few other oils with higher ZDDP levels available. Brad Penn oil has been recommended in the past. Personally, I don't recall the brand name right now, but I have purchased a high ZDDP motor oil at Family Dollar Store for the last few years. I can't seem to find it on the Family Dollar website at the moment, so I am not sure if they still stock it. I will try to find the name in the next day or so if possible. 


For brake fluid, you need to either use whatever is in it now, or even better flush the system, rebuild everything, and then use your choice. What is best to use for brake fluid will likely also result in many conflicting opinions.

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Eddie, our "General Discussion" category is excellent

for many questions--and gets the most looks and

responses--but I agree with Matt Hinson above,

that the Buick categories will get you good and specific

Buick advice whenever you need it for your car.

Look for the category "Buick--Prewar--Technical."


Some of our other categories, such as Nash and

electric cars, get few looks, and answers may not

come quickly, if ever.  But all the Buick categories

are well populated with knowledgeable Buick fans.


All the best to you with your new-old Buick!


Edited by John_S_in_Penna (see edit history)
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Never any novice or dumb questions here. Much better to be informed. I've been wrenching on all types of stuff for over 50 years and still ask questions. Sometimes it is because of old timers disease and just can't remember. Other times I'm still learning. Dandy Dave!   

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I was in the garage and looked at my oil to see what it was. It is American XT 10W-40 manufactured by the Warren Oil Co. LLC. It has served me well for thousands of miles in my 1937 Buick Century. I have not purchased any in the past several months,  but I have purchased it at Family Dollar Store (my only reason for going to Family Dollar Store). The funny thing is that doing a Google search for it, revealed that apparently Family Dollar Store has been sued in NJ for selling this oil as it is alleged to not be suitable for modern engines. 

Edited by MCHinson (see edit history)
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Apparently that lawsuit does not apply to American XT 10W-40 


Only to the 30W, not the multi weight. Because the 30W has no additives fro modern engines.


Additive Name    Additive Function
Antioxidants    oxidation control
Dispersants    varnish control
Antiwear agents    minimize valve train wear
Antifoamants    retard foaming
Anti corrosion    prevent corrosion (Fe)
Lubricity additives    improve metal wetting
Metal Detergents    keep surfaces clean
Viscosity modifiers    high temperature viscosity increase
Pour point depressants    allow oil flow when cold
Seal swell agents    ensure seals do not leak
Metal deactivators    reduce catalytic effect of metals
Corrosion Inhibitors    prevent rusting (Cu, Zn, Sn)
Extreme pressure additives     prevent scoring and seizure
Friction modifiers    reduce or increase friction


The 30W has none of these.


The photograph below is a close-up of AMERICAN XT SAE 30's back
label, which includes the warnings, "IT IS NOT SUITABLE FOR USE IN MOST


The 30W is grade API-SA which means no additives. API-SL has additives fro modern engines.


FINALLY there is PROOF !!!

In an internal report dated November 8, 2004 the "Alliance of Automotive Manufacturers" (Members at that time were: BMW, FORD, DaimlerChrysler, GM, Mazda, Mitsubishi, Porsche, Toyota and VW) compared the obsolete but still widely available API SA engine oil with in 2004 current API SL category (ILSAC GF-3).

The two oils were tested using two standard ASTM tests:

ASTM Sequence IVA  = low-temperature Valve train wear test
ASTM Sequence VG   = test for sludge and deposits

No surprise: the API SA oil failed both tests !


Oil Filter clogging, extreme scuffing on camshafts, oil starvation on cold start up.


"Engine life would be short, regardless of the oil change interval"

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