What kind of fluids for 1951 Cadillac 331 V8?

[Guest polonus]

I recently bought 1951 Cadillac Series 62 with 331 V8 and Hydramatic transmition.  I am going to run this car on no ethanol gasoline, however I am not sure about other fluids.

 

1. What kind of antifreeze should I use?

 

2. What about oil? Is synthetic OK? Any additives?

 

3. What kind of brake fluid?

 

4. Should I add lead substitute into gas?

 

5. What is in that Hydramatic AT?

 

Thanks for any help.

[Owen_Dyneto]

1.  The "green" or inorganic additive type, NOT the extended duty types (usually red in color) which are intended primarily for aluminum blocks and radiators.

2.  Collector cars usually don't see 10,000 miles a year and thus should have their oil changed annually regardless of mileage; thus synthetics offer little if any advantage.  Depending on the temperatures where you live and will be driving, a major brand 10-30 or 10-40 would be a good choice.  "Snake Oils" are usually just that and if you're buying an oil that contains ZDDP, DO NOT add more.

3.  Depends what's in the system now; if converted to silicone type, you must stick with it, ditto if conventional DOT 3 or DOT 4.  They are NOT mutually compatible and a changeover from one type to the other requires a complete system flush and replacement of all the rubber components.

4.  Not needed.

5.  Don't know what's in it now, I'd change it and the filter and refill with Dexron ATF.

[Marty Roth]

I recently bought 1951 Cadillac Series 62 with 331 V8 and Hydramatic transmition.  I am going to run this car on no ethanol gasoline, however I am not sure about other fluids.

 

1. What kind of antifreeze should I use?  --  Many opinions here, others will hopefully respond

 

2. What about oil? Is synthetic OK? Any additives?  --   If the car has been Well-Maintained, then use the same grade as specified originally, but I use Shell Rotella 15W-40 because of the extras. You should be able to use synthetics, but initially you may want to use conventional, and do frequent changes until you are satisfied with oil cleanliness. 

 

3. What kind of brake fluid?  --  DOT-4 mixes well with the DOT-3 which is probably in your system neow, but it may be a good idea to have an experienced friend help you flush and bleed the system first.

 

4. Should I add lead substitute into gas?   --  YES!  - I use Alemite CD-2 Lead Substitute, but there are many brands available. For its era, this was a high-compression engine, so while it may not be critical, in my opinion, it cannot hurt !

 

5. What is in that Hydramatic AT?  --  Not sure what you are asking here, but as far as transmission fluid, Type-A is not generally available so use the modern equivalent which is Dexron-Mercon in one of the newer types. 

 

Thanks for any help.

[Guest polonus]

Thanks for your advice.

[D Yaros]

There is no need for a synthetic oil.  Using such may cause more problems than it solves.  Synthetic oil is known to create leaks that mineral oil would not.

[Bleach]

 

4. Should I add lead substitute into gas?   --  YES!  - I use Alemite CD-2 Lead Substitute, but there are many brands available. For its era, this was a high-compression engine, so while it may not be critical, in my opinion, it cannot hurt !...

Thanks for any help.

 

 

 

This year did not have high compression. It only has about 7.5 to 1 compression ratio and will run fine without any additives.

Edited May 18, 2015 by Bleach (see edit history)

[Sweet64rivi]

Peak Green original green coolant. 

Brad Penn motor oil http://www.penngrade1.com/Zinc.aspx

[Rusty_OToole]

10W30 oil was introduced about the same time your car was built. It was meant specifically for your car and ones like it with the new OHV V8 and hydraulic lifters. Any good brand will work. The latest formulas have less zinc so some people prefer diesel rated oil which has zinc.

 

No need for any special gas additives. Your engine will run fine on the lowest octane regular. Some like to add a little Redex, Marvel Mystery OIl or your favorite upper cylinder oil to baby the rings and valves. But it is not strictly necessary.

 

Best advice is to get the original owner's manual and factory repair manual and follow the maintenance schedule. It was worked out by factory engineers to give the longest trouble free life.

[Bleach]

More details and specs, including a copy of the owner's manual. can be found here: https://www.gmheritagecenter.com/docs/gm-heritage-archive/vehicle-information-kits/Cadillac/1951_Cadillac_VVI.pdf

[Guest Bob Call]

The manual Bleach linked above says that for temperatures above +10 deg F to use 20W oil, from +10 deg F down to -10 deg F to use 10W, and below -10 deg F use 5W. So, you should us straight 20W or 10W-20, and in winter you could use 5W-20. A good brand like Chevron or Shell rated for diesel engines.

 

Antifreeze, use the Peak Green or Prestone Prime Conventional Green, only! New orange, red and yellow formulas are for newer cars with aluminum components and are harmful to the vintage iron and brass cooling systems like your Caddie.

[Matt Harwood]

There is no need for a synthetic oil.  Using such may cause more problems than it solves.  Synthetic oil is known to create leaks that mineral oil would not.

 

Not to single you out here, but synthetic oil does not CREATE leaks. The synthetic molecule is simply smaller (a long chain instead of a cluster) than an organic oil molecule, and therefore will fit through smaller holes than conventional oil. It is not creating leaks, it's simply finding holes already there and working its way through. Synthetics get a bad rep for this but it's not true that they're the source of the problem. It's just that old gaskets are a bit more porous than modern ones and this sort of "leak" doesn't indicate a problem with the seals. Just didn't want to keep spreading an old wives' tale.

 

That said, I agree that synthetic oil is overkill and unnecessary. You aren't seeing the engine speeds and temperatures where it makes a difference. The advice here is all good: use a quality conventional oil (I personally use Brad Penn in my old cars), change it annually regardless of mileage, and go by what the manual recommends in your transmission.

 

Coolant is problematic, because the color doesn't really identify what it is anymore. What you want is non-OAT antifreeze, which is the "old kind" but since manufacturers are playing games with colors, that's not a reliable indicator. Be sure to read the label. One of these days I'm going to switch to Evans Coolant and not worry about it anymore, but I just have to get around to it. Do some Googling on old car coolant and you'll find the information that you need, although it'll be confusing.

 

No need for lead in the gas. Over-blown non-crisis. Eventually the ethanol gas will cause something, somewhere in your fuel system, usually a fuel pump diaphragm or carburetor accelerator pump, to fail and you'll deal with it then.

 

For the HydraMatic, find the oldest Dexron you can; I've seen Dex 3 on the shelf at some auto parts stores. Dex 5 and Dex 6 are supposed to be backwards-compatible, but they're synthetic and may cause the leaking that I mentioned up above. Earlier stuff is just fine, just make sure it's clean and topped off. It's normal for the pump in your Hydra-Matic to moan a bit when it's cold, so don't worry about that.

 

Have fun!

Edited September 13, 2015 by Matt Harwood (see edit history)

[D Yaros]

Not to single you out here, but synthetic oil does not CREATE leaks.

 

I have big shoulders, so it is ok, you can/did single me out!    I'll accept your terminology, as it is a bit more precised than mine.  We both get to the same place, but took different paths to get there?