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Will higher viscosity oil result in higher oil pressure?

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  • Engine: Will higher viscosity oil result in higher oil pressure?

    I just changed oil in my 1950 Champion. I had 10 W 30 Mystik JT-8 (synthetic/dinosaur mix) and I changed to JT-8 15W40. Is it as obvious as it seems, that the thicker oil should result in measurably higher (according to my dash gauge) oil pressure? The higher pressure persists after warm-up.
    John
    1950 Champion
    W-3 4 Dr. Sedan
    Holdrege NE

  • #2
    Yes.

    jack vines
    PackardV8

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    • #3
      I agree. You might notice it will smoke a little more if your rings are worn.

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      • #4
        In multigrade oils... The first number is the cold 'pour point' number, and the second number is the high temp additive package protection number.
        So... It can pour cold like a 10 weight oil and give high temp film protection like a 40 weight oil.
        The 'W' stands for winter (again... low temp pour point)


        HTIH (Hope The Info Helps)

        Jeff


        Get your facts first, and then you can distort them as much as you please. Mark Twain



        Note: SDC# 070190 (and earlier...)

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        • #5
          Originally posted by DEEPNHOCK View Post
          In multigrade oils... The first number is the cold 'pour point' number, and the second number is the high temp additive package protection number.
          So... It can pour cold like a 10 weight oil and give high temp film protection like a 40 weight oil.
          The 'W' stands for winter (again... low temp pour point)


          http://www.shell.com/global/products...right-oil.html
          This is true,....but frankly, I've never completely understood how one oil can do this!

          (Best of both worlds)

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          • #6
            Originally posted by SN-60 View Post
            This is true,....but frankly, I've never completely understood how one oil can do this!

            (Best of both worlds)
            Actually, it's not the oil that does that. There are additives in multi-grade oils that form longer chains as the temperature increases. These have the effect of holding the oil molecules and keeping it from running off in high temps.
            Skip Lackie

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            • #7
              Originally posted by Skip Lackie View Post
              Actually, it's not the oil that does that. There are additives in multi-grade oils that form longer chains as the temperature increases. These have the effect of holding the oil molecules and keeping it from running off in high temps.
              Interesting and makes sense.

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              • #8
                All I have to go by is the standard dash gauge (0-40-80), but the needle is well above 40 at idle now, whereas it was below 40 before. An approximately 7-10 Lb. increase. I had not directly observed this phenomenon before, although it does seem obvious when I think about it.
                John
                1950 Champion
                W-3 4 Dr. Sedan
                Holdrege NE

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                • #9
                  I heard a good rationale to this once... " the higher the viscosity, the higher the resistance to flow"
                  64 GT Hawk (K7)
                  1970 Avanti (R3)

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                  • #10
                    Originally posted by Lothar View Post
                    All I have to go by is the standard dash gauge (0-40-80), but the needle is well above 40 at idle now, whereas it was below 40 before. An approximately 7-10 Lb. increase. I had not directly observed this phenomenon before, although it does seem obvious when I think about it.
                    You might check the oil pressure again when you've driven a thousand miles or so and see if the pressure is still higher than before. I suggest this because fresh oil of the same viscosity, that is oil that hasn't been contaminated with engine byproducts, will often show higher pressure than the same oil with mileage on it.

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                    • #11
                      I had the opposite problem. When we rebuilt the 289 that I put in my '53 we got the tolerances so close that it always pegged the gauge when cold and dropped to between fifty and sixty at warm idle. I was running Rotella 15/40. Changed to 10/30 and now at about 60 psi at startup and 35 at warm idle.
                      Brad Johnson,
                      SDC since 1975, ASC since 1990
                      Pine Grove Mills, Pa.
                      '33 Rockne 10, '51 Commander Starlight. '53 Commander Starlight
                      '56 Sky Hawk in process

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                      • #12
                        I do not understand why two of you use 40 weight oil. I recommend straight weight (20 or 30) for a 1950 Champion.
                        Gary L.
                        Wappinger, NY

                        SDC member since 1968
                        Studebaker enthusiast much longer

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                        • #13
                          For many years and miles, I used 20W50. I swapped over to 15W50 Mobil 1 about 17 years ago, and never any problems with either. I recommend either 20W50 dino oil, or 15W50 synthetic. I do not understand why anyone would use yester-decade, straight weight oil in anything other than a lawnmower.

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                          • #14
                            Originally posted by JoeHall View Post
                            For many years and miles, I used 20W50. I swapped over to 15W50 Mobil 1 about 17 years ago, and never any problems with either. I recommend either 20W50 dino oil, or 15W50 synthetic. I do not understand why anyone would use yester-decade, straight weight oil in anything other than a lawnmower.
                            I run Delo 15w40 in everything, including my lawn mower. Why would I go to the trouble of having more than one four-stroke oil for everything? If you'd rather run 10W30, 10W40, 20W50 or synthetic, I don't think there's any difference at all.

                            Today's oils are so much better than those of 60 years ago, any major brand is way good enough. Many of today's engines have change intervals of 15,000+ miles and any well rebuilt older engine can do the same.

                            Not only are today's oils much better, but the removal of lead from gasoline has doubled or tripled the life of spark plugs, rings and bearings, and exhaust systems too.

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                            • #15
                              Originally posted by JoeHall View Post
                              I do not understand why anyone would use yester-decade, straight weight oil in anything other than a lawnmower.
                              X2. I am very familiar (50 years)with a 1917 Studebaker SF4. In at least the last 30 years it has never had anything other than 10W30 oil in it with absolutely no ill effects.

                              Terry

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