5W-50 oil in 500 CI (1970 Eldorado) ? - Page 2
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Cadillac Seville / Cadillac Eldorado Forum Discussion, 5W-50 oil in 500 CI (1970 Eldorado) ? in Past Cadillac Vehicle Discussion; Originally Posted by Aztec ETC ECS I saw lots of sludgy engines in the 80's. Was it the thickness or ...
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    Re: 5W-50 oil in 500 CI (1970 Eldorado) ?

    Quote Originally Posted by Aztec ETC ECS View Post
    I saw lots of sludgy engines in the 80's. Was it the thickness or the quality?
    I guess it was a combination. Whatever additive they where using back then to take it from a 10 weight to a 30 weight, obviously needed that much more to take it to a 40 weight. I always suspected it was that additive that solidified and turned to sludge. Our old Guru confirmed that for me years ago and explained it better than I am. He also harbored the same feelings about 10W40 for the same reasons.

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    sgc2c is offline Cadillac Owners Member
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    So the basic problem here is one of high viscosity rather than low? That the 5 is all right (the manual does day as much) but the 50 is too thick?
    I used 15W-50 once for an OCI years ago without visible negative aftereffects.

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    Re: 5W-50 oil in 500 CI (1970 Eldorado) ?

    The bearings and "metal to metal" wear surface clearances in modern automotive engines (and your 1970 500 qualifies as "modern") are set during design and machining at certain values - in thousandths of an inch. Your 500 c.i. engine carries the same clearance specifications as a 472, a 425, a 383 or a 308. "Thicker" oil is not any more "oily" than 30 weight - it just won't flow through tight bearings as well, but it might be better for a high mileage/high wear engine.

    Lubrication and parts heat removal is done by oil flow; oil flow is created by pressure.......... and remember - your (our) oil pump has a pressure regulator system that limits it to about 60 psi max, cold. No matter what oil, within limits, you dump in you will never create more "pressure" or flow.

    Your last post - I'll bet your 500 c.i. engine would live a long, happy, lazy life running 10W-40 oil of whatever brand/type you like. If you're really anal about lubrication and what and why, get into some of the flame wars in the oil sites and see how other people get looney over "my oil is better than your oil".

    You might also want to do some research into the oil additive ZDDP, it's effect on flat tappet cams and lifters, and why some "modern" oils may not be satisfactory for your engine...... viscosity or mileage be damned: it's the additive package.

    Do you do your own oil/filter changes ?? Have you considered pre-filling the filter before installation to lessen the chances of a few seconds of oil starvation on startup after the oil change ?

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    Re: 5W-50 oil in 500 CI (1970 Eldorado) ?

    You might be OK with a 5W, but I'd stick with a 10W on a flat tappet motor.

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    Re: 5W-50 oil in 500 CI (1970 Eldorado) ?

    Here's a good explanation:

    http://www.upmpg.com/tech_articles/motoroil_viscosity/

    The way I'm interpreting it is- 5w50 is virtually unaffected by temperature, high or low- MAGIC Oil.
    Resists thickening when cold, resists thinning when hot.

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    sgc2c is offline Cadillac Owners Member
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    Yes I do my own changes and always fill the filter at least partially to avoid dry starts.

    With regards to ZDDP what do you recommend for the 500 motor?

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    Re: 5W-50 oil in 500 CI (1970 Eldorado) ?

    FWIW I run 15W-40 in my '70 Eldorado.
    Over here they call it classics oil... and I only drive it in the spring and summer when the weather is nice.

    I made the mistake putting full synthetic oil in the car which was the reason I had the engine completely overhauled bacause it ruined the valves.

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    Re: 5W-50 oil in 500 CI (1970 Eldorado) ?

    Shell Rotella is one that is supposed to have higher ZDDP levels. There is another one that starts with a D (Devron, Delcon, Delron, something like that), but the name escapes me. Someone will remember it. I think most any diesel rated oil also has higher ZDDP levels.

  9. #24
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    It's really safe and a good idea to use a diesel oil for a car like this? And I've used synthetic before (the aforementioned 15W-50 was Mobil 1). From a technical at standpoint how is synthetic detrimental to a motor like this?

    And are there any standalone zinc ZDDP additives or is the diesel oil really the best to use?
    Maybe something like an additive plus Mobil 5000 10W-40 would suffice? What do you think?

    I also routinely run about 8-10 oz of Marvel Mystery oil per tank fill-up and I use 93 octane, Lucas octane boost and a Gunk lead substitute as well.
    And recently I Seafoam'd it.

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    Re: 5W-50 oil in 500 CI (1970 Eldorado) ?

    Forget that ANY oil might be "diesel rated". Yes, it may contain more ash dispersant, but that's not bad. Otherwise, the Fleet/Marine oils are ALL rated for gasoline and diesel service - read the API oil classification bullseye on the oil jug.

    The flip side of "Is it really safe and a good idea ......." might be (in your case) "Is it really safe and a good idea to use a multi-viscosity oil specifically not recommended for my engine by GM ?".

    Don't believe ANY of us in here - do your own homework: Google "gasoline engine oil api designation" or something close. For starters - http://en.wikipedia.org/wiki/Motor_oil

    Who starts these old wives' tales about "diesel oil" and gasoline engines, anyway ??

    Figure out what "SL" means and what "CI-4" means.......... note that both are on the same bullseye ...........
    70eldo likes this.

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    sgc2c is offline Cadillac Owners Member
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    I KNOW what they mean. And we're up to SN now.

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    Re: 5W-50 oil in 500 CI (1970 Eldorado) ?

    If you know what the API designations mean, then what is the difference in additive packages for a SN automotive oil and a SL/CI-4 rated fleet oil ??

    We're fishing for ZDDP load and flat tappet cam protection.

    EDIT: Straight, honest question in open forum: Why on earth are you dumping all that unnecessary crap in your gas and engine ? All you're doing - and that's ALL you're doing - is driving up the cost of operating the car with no gains whatsoever. If you're sweating oils and engine life, look through this site - lots of good info. One of the HR oils in a 10W-40 (HR-4) would be just perfect for your engine - with nothing else added - ever.

    Read carefully, and note the context of "street", "modified", "blown", etc. in the oil descriptions.

    http://www.drivenracingoil.com/

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    sgc2c is offline Cadillac Owners Member
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    Are you saying that 43 years ago the types of regular motor oil one would've put in an Eldorado with a 500 motor contained that much more zinc than any oil conventional or synthetic (not specifically CI-4 high content) today?
    What's special about ZDDP for a 500 motor?
    This is the first forum in which I've ever heard it recommended for such an engine, and I've read hours of BITOG.

  14. #29
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    Re: 5W-50 oil in 500 CI (1970 Eldorado) ?

    Your first sentence: YES. ZDDP is a very necessary oil additive package used to prevent flat tappet and cam wear. Not so critical in our later roller cammed engines.

    EDIT at 6:55: BUT dumping in some off the shelf ZDDP snake oil bottle is NOT the way to happiness - just as in many things automotive, if a little is good, more IS NOT better.

    Google "automotive engine oil zddp calendar" or something close.

    Since 1999 the levels have dropped rather quickly........... and BITOG is subject to some rather radical flights of fancy - just as any online forum. You need to do the homework, not simply rely on someone's "I heard this from Joe's father's friend at Burger Doodle !".

    Here's a taste ........ read closely and interpret what you see.

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    What's your take on ZDDP additives like Rislone?

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