PROPER OIL FOR 346 CADILLAC V-8

[rmartin1]

Greetings All!

I have a question ... if anyone out there can answer.  I have a 41 Cadillac equipped with a 346 V8 engine.
We are doing some maintenance and repairs.  The question arises - what is the proper oil that should be
used in that engine?   We live in California so low temperature extremes are not an issue. However temperatures
can typicaly reach into the low 100's during the Summer months.  What weight of oil should be used? Also -
should this engine utilize DETERGENT .... or NON-DETERGENT Oil?  I've had a number of 38 Buicks over the
years. They required NON-Detergent oil.  Not sure when the Detergent oils were introduced. 

I don't want to use the wrong oil - soooo. if anyone out there has the correct information (which I'm certain
IS forthcoming) I would REALLY appreciate it!!!!  You can answer me here on this Forum ... or, if you wouldn't
mind - email me at my regular email .... ron@imageservices.co.  Best Regards!!! Thank you all in advance!!
Ron Martin, Modesto, CA

[Bobby B]

Ron,
Hi. Very Objective subject...I run Valvoline VR1 10W-30 or maybe 10W-40 in your Climate. Has enough ZDDP for your engine. Mixing ZDDP in with the oil is not the same as using oil with a high Zinc content. You can add it to regular oil, but according to a lot of studies, it needs to be heated up and mixed in, so why bother. Just go with the correct oil and save your time and money. Hope this helps...
            Bobby

[Bill Ingler #7799]

Hi Ron: I live in Arizona and use 10w-30. If you are a new owner to your car and have no idea of the history of that engine I would spend the time to drop the engine pan and see how much oil sludge has accumulated in the pan. I have seen pans where you needed to use a putty knife to scrape out the oil sludge in the bottom of the pan. The condition of the pan will give you an idea of how clean or how dirty is the top side of that engine.   Bill

[gary griffin]

Bill Engler is spot on with his recommendations.  These cars were built without filters and no added filter can possibly  fully clean the oil. Manuals of the time recommended removing the oil pan every year and cleaning it out thoroughly.  For most of us driving hundreds of miles a year instead of 10's of thousands of miles a year I would think annual oil changes and dropping the pan every few years should suffice!

[Carl Fielding]

Hi , Ron. There are 2 types of armchair amateur petroleum engineers. Those who have read Richard Widman's 33 page dissertation "Selection of the right oil for flat tappet engines" (most recent update March 12 , 2013) , and those who have not. Become one of the former. Most of this great work is understandable by most of us. All of it by many. The API or SAE tech journals from which this info has been distilled for our edification , would be beyond the capabilities of all but a REAL petroleum engineer. I recommend reading this from time to time , and am overdue , also have never done so on this forum. All of youse , STUDY UP ! Now , there is a bit more to this particular subject at hand. A given engine will have something to say about the oil selection and change frequency sequence. So : as Bill says , drop that pan. While you are slumming around in the basement doing your maintainance and repairs , check those bearings. Pull a couple of rod caps and a main cap. Hopefully someone intimately familiar with the monoblock flatheads will tell us which main is the most vulnerable. Rear ? If there is minimal pitting and scuffing , and plastigage shows you are within spec , zip it up. Anything marginal ? Check 'em all. Any noisy (dirty ?) lifters ? Hey , if all is reasonably clean and tight , you have the option of using a superior , modern , multi grade , detergent , synthetic oil. (Remember : READ WIDMAN). Oops , something has come up that I must deal with. I'll be back , but it might be a day or two. More about filtration and oil change (cleaning sequence) to come.  - Carl

[marty55cdv]

I am on the Valvoline VR1 team with Bobby, I use 10w30 and or 20w50

[Carl Fielding]

Marty , 20W/50 in what vehicle under what conditions ? Please read "Widman" , referenced above. Pay particular attention to the temperature/viscosity operating envelope of 20W/50 engine oil. I use it in my slow , loose old Cadillac (1924 & 1927) engines. I do use Amsoil , perhaps the most synthetic of synthetics , with plenty of zinc and phosphorus. BTW , C*****l seems to be about the least synthetic of synthetics. I am sure this will be seen as provocative by some , but do take the time to study "Widman" thoroughly. I thought I knew enough about oil until I did so. Just like I thought I knew how to adjust my rear view mirrors until I took an all day safe driving course in the classroom and on the racetrack. Old dogs , even this ancient mutt , can learn new tricks ! Makes you feel more alive. Might even keep you that way a bit longer ! I promise that if I myself remain in that mode for a few more days , I will finish what I started above. I just hope enough interest and suspense is generated , so as to convert a few more Widman fans. Anyone here who already has studied those 33 pages ? - Carl

[savemy67]

Hello all,

Carl,  I "googled" Widman and found a 33 page document titled "Selection of the Right Motor Oil for the Corvair and other Engines", By Richard Widman.  Is this the paper to which you refer?  Thanks.

Christopher Winter

[Carl Fielding]

Yes. You will see this applies to all engines. For me , with my declining mental faculties , it takes several readings in places. Concentration and memory somewhat impaired. I had some of my oil opinions corrected , and should inquire of Richard Widman whether my inferences and extrapolations are on the mark. For example : is my use of 20W/50 in my 90 year old engines optimal , although out of the temperature/viscosity envelope ? Some of my reasons for using a superior synthetic include the fact that all engines have hotspots , and with the significantly higher flashpoint of synthetic , you have a greater margin of safety in case of overheat. Saved my overheated (cracked both exhaust manifolds) '76 Eldo many years ago. I still get to drive it , sometimes aggressively , out on the wide open , lightly travelled , Western highways and byways. Please let us know what you think of your 33 page studies ! - Carl

[fishnjim]

Lots of people have the same problems when it comes to motor oils because they have only the owners manual or marketing info to listen to and what their buddy uses or swear by or at as I say. 
There's some good info in this study, but I don't like some of the statements based on technical points.   Why would you want to use the factory recommended oil when the gasoline you use is much different than back in the day?   I've not understood that logic.
The best thing to do as he mentions is monitor the oil.   This does not have to be an analysis per se, but check the dip stick every 500 or so miles and observe the color and slipperyness/grittyness of the oil.   If you don't drive enough for an oil change in a year, change it anyway.   Start with a clean motor and keep it that way.  If it's a no filter engine, change often and clean the pan.   No additive or oil is going to repair damage or prevent damage from misuse.   
I like the don't put under stress until it warms up.   The "old timers'' used to rev it up when they started.   This is bad, and worse on a no oil filter motor.  Majority of engine wear occurs during starts.   The camp that put the high vis and/or additives in are fooling themselves.  Widman makes a good case for not doing that.   I've covered this subject in several forums as well.  They sell high ZDDP vintage oil, but the amount of ZDDP you need and the amount that's used up between oil changes doesn't warrant it.   But there's a loyal/swear by it collector car following.   The old cars were made and operated in a time when the art of oil and motors wasn't as sophisticated as it is now.   Use rate, HP, gasoline, and materials were at a different standard.   But then, like now were subject to marketing claims.  Some of it is to cause confusion in the hopes of staying brand loyal, some it to counter the competitions claims.