Best Conventional Motor Oil For Our Older Cadeillacs

[EAM 17806]

What would be the best conventional motor oil we should be using for our 1970-1979 Cadillacs with 492/500 cu engines.  There seems to be a lot of concern with the amount of zinc additives that the manufacturers put into these oils. I have considered the following conventional oils to be quite acceptable, what are your thoughts?:  10W-30, Castrol GTX, Valvoline Premium, Pennzoil, Havoline Shield and Mobil Super in that order; I'd appreciate your opinions and how you evaluated your decisions.  Remember, the reduction of ZDDP in oils for 1975 up for catalytic converters being affected!.   EAM

[Jeff Rosansky CLC #28373]

Boy is this going to open a can of worms
I know a few old car guys, mostly Corvettes.they use Quaker State Defy. That's what I use too $15 for 5 quarts at  Walmart.
Jeff

[rlachance]

lets open up another can, what about an additive like Lucas???

[Jon S]

Penzoil or Quaker State 10W/40 (both manufactured by the same company) with ZDDP or Red Line Break In Oil (for ZDDP protection) will serve just fine.  You can spend more money for other oils, but why?

[cadillac ken]

Flat tappet motors (like the, I think you me the 472--500 ci.) do need the added ZZDP.

I only use Joe Gibbs racing oil or Brad Penn.  Do a search and you will see why.  No need to add anything with these oils.  They are formulated for the flat tappet protection these motors need.

I order mine through Amazon.  FWIW.

I use it in all my old cars.  I recommend it to all my customers who I build cars for that have flat tappet engines-- old motorcycles too.

[fishnjim]

There's a 2 letter code on the oil that identifies its service.   If you can't get what the manual sez anymore then for the most part the later oils will meet the earlier service.   Also depends how many miles.   If it's a fresh rebuild, I'd go back to what the manual called for in terms of viscosity.  Alot depends on how it's driven, highway vs stop and go and other factors as to how frequently to change.   If it's high mileage, I wouldn't switch oils unless I pulled the valve cover and pan and observed how much build up is in there.   If it's clean, then you're using the right stuff and no need to switch but safer to do at that point.   If its crusty in there, well, wrong stuff, infrequent change period, or needs work that oil won't solve.  If you put something in that dislodges alot of buildup you can plug the passages.
re: zinc.   That's pretty much the prewar era with "high" levels.   After they figured out they could cut down the zinc and use other additives it's not a big factor.   Somewhere I have a graph that shows how much zinc is used up per mile and even in the low stuff there's like 10 times what would leave in a normal oil change period, so adding alot more is wasted.   They had different bearing materials and other mechanicals that no longer exist also.   Most of these early motors were meant to change the oil frequently because it was cheap in those days and weren't filtering the oil either, so no telling what went on in there.   Mostly sludge buildup - probably from too much zinc...and leaded fuel.

[76eldo]

I use Lucas Hot Rod 10/30.  It has the zinc additive pack in the formulation of the oil.

Brian

[Maynard Krebs]

With me, old habits.. never die.

I use Valvoline 10W-30.   I concede that it's not cheap, and my son questions my judgment of continuing to use it; but that's what I use..... and have for about 45 years.

[64\/54Cadillacking]

Valvoline Racing oil, 20W50. It's not too expensive either, and you'll probably wont even need to add a bottle of Zinc additive to the engine since the oil itself has plenty of it.

You can find this stuff at most auto parts stores.

[Scot Minesinger]

I use 10 W 40 Pennzoil from an Auto parts store and add ZDDP from Eastwood.  39k (90k rebuilt engine to now 129k miles) miles later she is still doing great.  Back when I was in high school (1976-79) everyone upgraded from 10 W 30 to 10 W 40 and ZDDP was in there already.  In the 1960's and 1970 I don't think 10 W 40 existed and so manufactures recommended the 10 W 30 instead of 10 W 40.  Got very high mileage out of my mid to late 1970's V-8 engines using this oil, changed every 3k miles.  However on my 1970 Cadillac I change the oil every six months unless mileage exceeds 3k miles.

[Jeff Rosansky CLC #28373]

This is off topic but because this thread was brought up I will post it.
I have a 100K Accord that would burn about a quart/thousand miles. Honda has a recall on this because of stuck oil rings. I have always used 10w-30 in it. The dealer says Honda now recommends using 0w-30. I had it changed there and it hasn't used any in 2k miles.
Jeff

[EAM 17806]

Valvoline Racing oil, 20W50. It's not too expensive either, and you'll probably wont even need to add a bottle of Zinc additive to the engine since the oil itself has plenty of it.

You can find this stuff at most auto parts stores.

I would think that 20W-50 oil would be just too thick for our 70 cars. No service manual for these 492/500 cu engines come close to suggesting this viscosity  that I'm aware of.  I personally wouldn't use it in my 76 deville, but to each his own.  Everett

[35-709]

Indeed the shop manual DOES recommend 20W-50 oil for the 472/500 engines.  Page 0-21 of my 1973 Cadillac Shop Manual recommends 20W-20, 10W-30, 20W-40 and 20W-50 for all temperatures above 20 degrees F. 

After overhauling the 472 for my '73 Caribou, MTS recommended 20W-50 Valvoline Racing Oil.  I used that for a while but switched both of my 472s to 15W-50 Mobil 1 since it also has adequate levels of ZDDP and I consider it to be a better oil.  To each his own. 

[Carl Fielding]

Gargoyle up : "Selection of the Right Motor Oil for thr Corvair and Other Engines". The author , Richard Widman has written the most knowledgable paper for the non-petroleum engineer reader. He is a genius of a petroleum rep. This 33 page masterpiece is distilled from S.A.E. And A.P.I. tech journals. (Ever try to read a tech journal outside of your field of Ph.D expertise ?). You may have to read parts of it 2 or 3 times , as I had to do. Fascinating. Ev , why do you say "conventional" ? Are you trying to save money ? Save your emgine ? Synthetic ? Turns out there are different degrees of syntheticity. Castrol barely is , Amsoil at the top , with Mobil 1 at about half mast. (No , Widman does not rep Amsoil). Amsoil has a line of multi-grade synthetics with the right amounts of zinc and phosphorus. Draw your own conclusions re: 20W/50 after reading. Myself ? I lightened up. Of course , if you are in some extreme temperature environment , this has some bearing on viscosity choice. Oil temp gauge ?

Jeff , VERY interesting ! Hardly off topic. Seems that Honda engineers understand state-of-the-art multi-grade lubricants quite well ! Imagine that ! Are you/have you been using synthetic ?
                                Your forum friend , Carl

[76eldo]

There was a tech seminar at the GN at Lake George held by a professional engine builder.

He said that engines built since the early 90's have roller lifters but the older flat tappet cams and lifters need the zinc in the oil to assure good lubricion between the cam and lifters.

He also said that you should stick to oils that come formulated with zddp because all oils have additive packs and if you add a zddp additive it may or may not be compatible.

I have been using Lucas Hot Rod oil since then.

How about Shell Rotella? Does that have zinc?

[David King (kz78hy)]

This is what I use:

http://www.classiccarmotoroil.com

Point and click and it shows up at your door.  Good stuff and designed for older engine design that does not get a lot of use.

David

[Driver8]

for my '79 Seville, (Oldsmobile 5.7 V8), it's Royal Purple all the way.  I order the oil/filters on Amazon.

Mark~

[dadscad]

I've been using amsoil full synthetic oil in my 63 since 2002. I used 0-30 until the reformultion mandate, then switched to the HDD 5-30 that has the right amount of zinc and phosphorus already in the fomulation, no additional additives needed.

[RobW]

1973 owner's manual....

[Carl Fielding]

I have run 20W/50 and 15W/50 , full SYNTHETIC oils in my 472/500 Cadillacs , and 460 Ford vans for many years , and hundreds of thousands of miles. If not for this , I expect I would have lost the mill in my daily driver '76 droptop. Hot day , hard drive , munged-up radiator. Overheated , cracked both ex. manifolds. Cooled down , slowed down , new 20W/50 SYNTHETIC (this  means no  Castrol) . New radiator and many years and tens of thousands of miles later , still running strong. If I still drove like that in heat like that , I would not have lightened up at all. That oil saved my "Kitty". Funny , isn't it ? Technology never stands still ! Better cars as the decades roll by. Oil and tires too ! Whadda ya know !  -  Carl