0W-40 in 1970 Cadillac Eldorado

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I've got a great old 1970 Cadillac Eldorado. The 500 CI motor at its highest-rated-ever 400 HP.
Living in the Northeast, it's cold here a lot of the year, especially
in the morning. Though I hardly ever start it up on a cold morning, I wonder about the overall stress and strain to the engine when it's bone-cold out there and I'm using (typically) 10W-40 motor oil. I've used synthetic and conventional at times, and even 10W-30 here and there. None of them have caused any noticeable problems.
Would switching to something like Mobil-1 synthetic 0W-40 be a good idea to get the oil flowing quicker and more easily to the various engine parts in cold weather? I ask because the only cars which are ever recommended for usage of 0W-40 seem to be European luxury and sports sedans, not this classic road barge of old. Plus Mobil-1 in particular seems to be recommending the "0W" grade wherever the "5W" or "10W" would normally be used such as to promote better cold starts and increase fuel economy. This, especially with its "Advanced Fuel Economy" line of oils (e.g., use 0W-20 where you'd normally use 5W-20). Although since #W-40 oils aren't offered in that line, I'd consider regular Mobil-1 0W-40. Any advice on this? Good idea? Bad idea?
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All I can say is try it and find out. I did try the 0W40 in my 944 once and found that it thinned out at high engine temps enough to noticeably drop the oil pressure as indicated on the gauge. 5W40 syn would not do this. If you have an oil pressure gauge try it for a bit and see what happens. Be aware that if you switch from dino squeezins to syn you may notice an increase in seal/gasket leaks, even though the oil mfgrs. have done a lot to mitigate this from the 1st gen of synthetics.
nate
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An enviable car, as long as gas doesn't go back up to $4!
I'd say that: * Switching to a synthetic or a high-detergent (fleet; diesel) oil on a non overhauled "survivor" engine that old is asking for trouble. * It's coming up on its 40th birthday and counting, so what you've been doing plainly works. * Although large and powerful it is not a highly stressed engine. * There was a fair bit of sophistication in motor oil by 1970; most of the changes since then have been responses to problems that evolved since then (hotter-running, higher-revving engines, pollution concerns, etc.) * Looking to advanced and/or lighter motor oils to improve the fuel economy of a 1970 Eldorado is like firing the aft guns to improve the fuel economy of a battleship. * Any car of that age is likely to dirty its oil faster than a modern car in good condition.
I might go with a "high mileage" conventional (dinosaur; non- synthetic) 5W30 if you are concerned about cold starts for what little driving you do in winter, 10W40 like you've been using in summer, changed every 3000 miles with a quality new filter. And many more happy years of cruising!
One man's opinions, worth what you paid if your ISP is inexpensive, --Joe
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It is not wise to switch tyhpes of oil. Synthetic is great if you never use regular oil. If you have ued regular oil, stick with it. With that engine, I'd suggest you use an arctic grade oil unless you are going to drive lots of highway mines. Then a goof 5 w30. Texaco Havoline is good. Shell has gone good oils as does Castrol. AVOID standard Pennzoil or Quaker state in that engine. There are some other good oils out there. If you ever do a complete rebuild of the motor, stick with a good Synthetic like Mobil 1.

Not at this point when you have used conventional oils. Only if you completely tear down the motor, at least hone the cylinder walls and give the block and all parts a good bath. I know there will be folks who will disagree with me on this point, it has been my experience that convention oil and synthetics don't mix. Pick one and stick with it. There are good and bad in both. The whole issue of multiple viscosity oil is largely a myth. There are laws of fluids. All fluids are thicker when cold and thinner when hot. All this multiple viscosity crap does is plays with the clock. How much time it takes to get thick and thin.
< I ask because the only cars which are ever

The Mobil 1 is GREAT oil. You won't blow up your motor using it or anything, but the residue conventional oil will act like a contaminant in it. You won't get the performance you would have in a new engine. I can't recommend any oil higher than Mobil 1. Castrol Edge is pretty spectacular as well.
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Interestingly, the manual for this car (which is close to 40 years old) specifies a rather wide variety of grades for this car. I have to believe they were vastly different in 1970 so I pay it no mind.
Everyone always said "10W-40" as the default response for that car. Can 0W-40 be anything (significantly) different other than it's viscosity at cold temps? I think of 10W-40 and 10W-30 (which I've used occasionally in the past as well) as identical at cold temperatures. Speaking of temperature, about how hot DOES this kid of car run? Everyone talks about cars "running hot" these days. Is this relative? Did cars "run hot" back then? This is a 500 CI motor after all. I just don't know.
I've used 15W-50 Mobil-1 synthetic and other grades of conventional oil (10W-30 up to 20W-50) before. None produced any ill effects that I can report. The engine does leak oil to a degree and none of those oils made it better (or worse). My real question is would 0W-40 make for easier starts in the cold? I want to make the engine last (never have to rebuild or replace) so synthetic is an option I'm thinking of returning to, and perhaps 0W-40 is the right grade for every situation. But if people have other ideas, I'm always listening.
I have found the posts so far very imformative: a big thanks to N8N, KRP and Ad absurdum per aspera.
-The Derfer
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Interestingly, the manual for this car (which is close to 40 years old) specifies a rather wide variety of grades for this car. I have to believe they were vastly different in 1970 so I pay it no mind.
Everyone always said "10W-40" as the default response for that car. Can 0W-40 be anything (significantly) different other than it's viscosity at cold temps? I think of 10W-40 and 10W-30 (which I've used occasionally in the past as well) as identical at cold temperatures. Speaking of temperature, about how hot DOES this kid of car run? Everyone talks about cars "running hot" these days. Is this relative? Did cars "run hot" back then? This is a 500 CI motor after all. I just don't know.
I've used 15W-50 Mobil-1 synthetic and other grades of conventional oil (10W-30 up to 20W-50) before. None produced any ill effects that I can report. The engine does leak oil to a degree and none of those oils made it better (or worse). My real question is would 0W-40 make for easier starts in the cold? I want to make the engine last (never have to rebuild or replace) so synthetic is an option I'm thinking of returning to, and perhaps 0W-40 is the right grade for every situation. But if people have other ideas, I'm always listening.
I have found the posts so far very imformative: a big thanks to N8N, KRP and Ad absurdum per aspera.
Having had one of those glorious beasts Eldorado with the 500. . . I can say they are particularly delicate motors. It was not one of GM's better offerings. Neither was the pain on the Eldos, particularly the metallic. I think the engine would do okay today if you had a new one and stuck with oil like Castrol Edge. For some INSANE reason, it seemed like many people used Pennzoil and Quaker State in those engines. By the time they had 50,000 miles they were full of sludge. Cylinder walls horribly varnished and scored. They were blowing oil like mad by 65,000 miles. Seems like people with other GM vehicles were not as prone to use that crappy Pennsylvania oil. Don't switch. Use a major brand conventional oil. Like I said Texaco and Shell have really good, inexpensive oils as does Union 76 and Phillips. Stay away from the off brands and chain store oils. (K-Mart - Wal Mart etc) House brands. Castrol makes really good oils too.
The 500 isn't a bad engine if you care for it properly. Like I said, if you got a new 500 it probably would hold up well. GM engines of 1970 generally weren't the best. That was a dark period for American cars in general.The bad American cars of the 70's is why you see so many Japanese cars today on our roads. Detroit was largely building "shit." The engines had all that emissions crap on them that really didn't work well and burned valves etc. Rube Goldberg devises thought up by Ralph Nader types who had NO idea what makes an automobile run. That is another reason Japan & Company got 55% of the American car market. Japanese cars didn't have to have all that crap sucking the life out of their motors.
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Lots of things have changed with engine oil over the years but but the weight still means what it meant. Your chart in the manual is still good.

It takes more viscosity modifiers in the oil to get the larger spread. As the oil ages the viscosity can drift off. My understanding is this isn't as big of an issue with synthetics as it is with regular oil

Stock thermostat was 195. The temp goes up to 220 ~ 230 on a hot summer day idling in traffic.

higher than what you would have seen in the old days. A new car may not even turn on the fan until 220 degrees. Your Cadi's cooling system is getting is working as hard as it can and loosing ground around this temp.

Yes 0W-40 can make it easier to start in the cold. What kind of cold are you talking about? Is this your daily driver? Personally if I wanted the engine to last forever I wouldn't be starting it at all in temps where I was worried about oil flow. Will the oil make any difference long term? Well I guess you pick your pony and take your chances on that one. I would pick one oil and stick with it though and quit doing this multiple products and multiple weights stuff.
Honestly at this point in the cars life what you do today isn't nearly as important as what has been done to it over the last 40 years. On the plus side the 472/500 was, IMHO, one of the best engines to ever come out of General Motors. I have had several that were poorly maintained with a gazillion miles on them and you just can't kill them. Now the CV joints... that's another matter alltogether and I wouldn't wish them on my worst enemy!
Steve B.
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You may wish to investigate GM EOS or Shell Rotella - something high in zinc for your engine, especially if you want it to live forever.
http://www.hotrod.com/techarticles/engine/flat_tappet_cam_tech/cam_construction.html
Ray
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Shell Rotella is a GREAT oil for that engine.
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Again, I have tried the Rotella synthetic 5W40 in my Porsche 944 and found the Mobil 1 of the same grade to hold higher oil pressure at speed. just my experiences... have not experienced this with cooler- running Studebaker V-8s however (those I've been running the regular dino 15W40 though.)
nate
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Again, I have tried the Rotella synthetic 5W40 in my Porsche 944 and found the Mobil 1 of the same grade to hold higher oil pressure at speed. just my experiences... have not experienced this with cooler- running Studebaker V-8s however (those I've been running the regular dino 15W40 though.)
There are two Shell Rotella oils. One is a high quality conventional motor oil. That was the one he was referring to. It is an extreme duty oil used lots in trucks.As far as synthetics, until Castrol came out with "EDGE" Mobil 1 ruled the roost. There are several GOOD standard motor oils. The problem with the Eldo 500CID is that in the 70's it was burdened with lots of Ralph Nader imposed gee-gaws that really screwed the motor. Get all the crap off it, set it up right from a fresh build and it's a great motor. Well, at least a good one. I had one, they regularly ate valves among other things. Plus the Eldo was a bloated turkey 900 tons and really junk front wheel drive. It was a nice riding car, but NOT a pleasure to own. The paint on the 70's Cadillacs was also awful. Mine was medium metallic blue. it cracked all over like a cheap egg. Nothing you could do but strip it to bare metal and work your way back up. GM repainted mine several times. The last time they authorized taking it to bare metal. Both the primer and paint were crap, so I bought some BASF primer and used FORD paint. It didn't crack again. Oh and the CV joints. MAYBE 10,000 miles before they started playing loose marbles in a can. It really wasn't the best car Caddy ever built.
Try Castrol Edge in your pound puppy, you'll like it.
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But the regulations and devices you speak of are all post-1970, right? Cat converters etc came out later in the 1970s (so I thought). Am I right? This car took regular gas. I add lead substitute once every few tankfulls. (Should I add it more often?)
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Unless the car was originally sold in CA all it would have on it would be a PCV valve (which only cycles the crankcase vapors back into the intake with no/insignificant performance loss). Maybe EGR, but I think EGR was later than '70.
49 state emissions didn't get air pumps and the rest of the add on's until the mid 70s. They got really bad for '75 up models.
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EGR was introduced 49-state in 1973. (Not sure about CA.)
Catalytic converters were first introduced by GM in 1975, but catalyst-free new cars were still being sold as late as 1980. (Those used gadgets such as air injection into the exhaust to burn up hydrocarbons.)
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Roger Blake
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wrote:

My 74 had all that crap on it.
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Why is Mobil-1 0W-40 referred to as a "Eurpoean Car formula"?
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To sell OIL?
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My Eldo was a 74 it had so much CRAP under the hood you barely could see the engine. PCV and all that crap. I am not sure of 1970. But by 74 the engine compartment was filled with junk. Mine took Premium. Regular would knock like a diesel. I thought Tony Orlando was under the hood. (Knock 3 times.) Could NOT keep CV joints on the car. Today it makes little difference, you have to add a lead substitute or the valve stems burn up. Lead was a lubricant. All in all it was NOT Caddy's best effort.
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do you really want to take mechanical advice from a guy who purchased his education online?
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do you really want to take mechanical advice from a guy who purchased his education online?
Il mittente di questo messaggio|The sender address of this non corrisponde ad un utente |message is not related to a real reale ma all'indirizzo fittizio|person but to a fake address of an di un sistema anonimizzatore |anonymous system Per maggiori informazioni |For more info https://www.mixmaster.it
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