Motor Oil for the 500
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500, 472, 425, 368 Discussion, Motor Oil for the 500 in Cadillac Engine Technical Discussion; does anyone know what the original manual called for for oil? 10w-30 or 10w-40? anyone have any expeiriance running synthetic ...
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    76CaddyHearse's Avatar
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    Motor Oil for the 500

    does anyone know what the original manual called for for oil? 10w-30 or 10w-40?
    anyone have any expeiriance running synthetic oils? probably going to make the switch next time i change oil/filter.

    and one more question while i'm asking about oil, my cad sits about a week in between starts. when its cold and I first start i can hear the engin "knock knock until the oil builds pressure then gets up in the motor. know anyway to prevent this? would just starting it like every other day help this?

    thanks!

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    Re: Motor Oil for the 500

    I have the same problem with the knock and would also like to know the answer to this.

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    Re: Motor Oil for the 500

    From a great source:

    "If you use shelf passenger car oil ,such a Castrol, Valvoline or any other, it has no zinc because it ****s with converters and O2 sensors. You can use Rotella or Dello 400 which are designed for diesels and still have all the neccesary supplements or use shelf oils of your choice and add a zinc supplement EVERY oil change. I think the Comp # is 159 and is an 8 oz bottle. If you don't do this, you could be slowly killing a cam. This does not count for rollers, only flat tappets. The reason synthetic shouldn't be used is that it is too slick to cause the lifter to spin correctly and it sits still and wears a groove in it, also killing the cam. All this stuff was designed before the synthetic and low or no zinc oils and only suffers because of our ignorance. Just thought each and every one of us would benefit from that little piece of info."

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    Re: Motor Oil for the 500

    interesting, zinc i guess helps the oil bind to the metal in of the upper parts of the motor better. whelp i'd rather destory my cat then my cam!
    the O2 sensor is for emission controls and efficiency, its on the exhaust manifold, no? i think it got kicked to the curb when i put on my headders. a well tuned carb really doesn't need one, a?
    thanks for the heads up on synthetic oil, i won't go that way now!

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    Re: Motor Oil for the 500

    You never had an O2 sensor. What it is is the older motor oil, at the time that these cars were made, had the zinc. Now most oil, espeically synthetic, is made without zinc because it messes up the newer cars O2 sensors, and lots are OHC, etc. The oil made for diesels still has the zinc though, and is what a lot of people use in these old caddys for the reasons described above.

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    Re: Motor Oil for the 500

    thanks, yea i didn't remeber if i had dissconnected a o2 sensor, guess not!
    i'll see what i can find at the autoparts store.
    thanks for the great advice!

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    Re: Motor Oil for the 500

    I use 10W-30....

    I have heard 10W-40 isn't good due to some small oil passeges....

    I usually use Mobil, or Castrol GTX High Mileage... on the '79 I kinda use any good brand. I tires Mobil 1 synthetic (what the '93 4.9 gets) and it started to leak from the rear main, so I switched back....all better now.

    These engines hate to sit, if they sit long enough (6 months or so) the wrist pins will actually seize causing piston slap, and a loud knock.... that is the exact thing that happened to my 425, the guy thought the engine was blown, it was knocking loud... I got the car for $300. My grandfathers '71 Fleetwood limo with the 472 knocks also (never used anymore) it just needs to be driven.

    That knock/tap on startup really can't be fixed AFAIK, just live with it, it really isn't bothering anything, and on my 425, it is only for the first 3-5seconds or so.

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    Re: Motor Oil for the 500

    Quote Originally Posted by terrible one
    You can use Rotella or Dello 400 which are designed for diesels and still have all the neccesary supplements
    Except that they are also designed with diesel weights. 5W40 should be fine, but 15W40... Well, maybe when it is really hot in summer... Our engines were designed for 10W30, not the thicker stuff.

    Seriously, that stuff about synthetic is not true though. I have synthetic in my Camaro and you can see the pushrods turning with the motor running, indicating that the lifters are spinning as intended. Plenty of people run synthetic oils with flat tappet cams with no problems at all. Honestly, if the synthetic oil reduces friction so well that the lifter isn't spinning, how in the world is there enough friction to wear a groove in there? Now, I have heard not to break in a motor on synthetic, but once broken in it is fine.

    I also have Mobil 1 in my 472, and no strange noises whatsoever. The car also usually sits for awhile between drives since we don't take it out all that often.

    Synthetic oils tend to stay longer on metal parts protecting better on a cold start, especially when the car hasn't been driven for awhile.
    Zinc in an oil doesn't have anything to do with it sticking, but provides an extra layer of protection. Basically, if the oil film ges pushed aside, you've got a tiny bit of zonc there to wear on before wearing the actual part that is being protected. Check out www.bobistheoilguy.com

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    JTraik is offline Cadillac Owners Enthusiast
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    Re: Motor Oil for the 500

    Grand Statement #83475028389025

    Quote Originally Posted by Night Wolf
    These engines hate to sit, if they sit long enough (6 months or so) the wrist pins will actually seize causing piston slap, and a loud knock.... that is the exact thing that happened to my 425
    What other engines has this happened to?

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    Re: Motor Oil for the 500

    I would heartily recommend the use of 15W40 in your 500. This is perhaps the best oil out there. Period.

    I am still not a convert of synthetics. While they are more finely engineered, they are still from base hydrocarbon stock. The hydrocarbon strings are more uniform and stable that the random strings in conventional oils, but thery are still subjected to the same conditions, and can all feel the same effects. They get around this with more complex additive packages.

    ZDF is very beneficial to any flat tappet engine, or any engine for that matter. But higher concentrations of it ccan adversely affect convertors, particularly if your engine does burn some oil. But for these older engines where the convertor is usually not there anymore, or never had one, these oils are the best way to go.

    They are designed particularly for HD truck and diesel applications where drain intervals are often in the 50,000 mile region. Plus the new EGR diesel engines put extra strain on the oils. These oils have to overcome some of the most extreme duty cycles out there, and they are engineered for that. Because of this, they are a good choice for our car engines.

    Personally, I have been using 15W40 HD oils in all of my cars for 25 years. I have never had any engine concerns. Never.

    An additional benefit would be to add a can of EOS periodically to your engine at oil change time. This has a very high concentration of ZDF and can actually repair minor galling and wear.

    As far as the engine knock at start up is concerned, I would investgate your oil filter. You need a filter with an anti drainback valve. This prevents oil from draining out of the passages when it is shut down. The brand of filter is also important. Stay away from Fram or any filters that they manufacture, such as Pennzoil. They are very cheaply constructed and offer the lowest filter medium area of most any filter out there. I use AC/Delco filters. They have a very good cost/benefit ratio. Another good choice would be Hastings or Wix.

    Mike

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