Gentlemen: What motor oil do you use?

Slant 6 Engines

  1. cruiser

    cruiser Well-Known Member

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    Hi Guys: I have a 1974 Duster with the slant six engine. What is the best motor oil (weight and brand) to use in this motor, and why do you feel this way. Please also mention how often you change the oil and filter. Right now, I'm using a NAPA Gold filter, and they work great. Your thoughts?
     
  2. Naplm00

    Naplm00 Well-Known Member

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    I live in a warm part of northern California. I use delo 15/40 sn/ck oil and a wix 51460 filter.

    Filter is slightly narrower and taller then a standard filter and had an internal standpipe as mine is missing. Makes for instant oil pressure at startup and it's easy to install on my 64 dart.

    I change it every 3k.

    We have a 84 diesel rover that has done 650,000+ miles on one engine rebuild, uses the same oil.




    Edit :. Get ready for a TON of strong opinions !
     
  3. Jax_1975_Dart

    Jax_1975_Dart Well-Known Member

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    +1 for the Wix filter. I run basic Dino oil 10w30 (live in FLA). Change every 3,000.
     
  4. TrailBeast

    TrailBeast AKA Mopars4us on Youtube

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    Any half way decent oil is perfectly fine and the Napa Gold/Wix filters are about the best you can get as an off the shelf filter.
    I run Castrol 5-30 full synthetic in the 5.9 but I wouldn’t run it in a slant or LA motor, as they were not machined to run thin synthetics.
     
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    • flingdingo

      flingdingo Well-Known Member

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      I'm with Naplm00, 15-40 Delo (or Shell Rotella, one or the other is usually on sale at O-Reillys) and a Wix filter in my Slant.
       
    • ch1ll

      ch1ll FABO Gold Member FABO Gold Member

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      Call your local amsoil dealer. Best oil products money can buy. Tell him what you got and he will hook you up.
       
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      • dartfreak75

        dartfreak75 Restore it, Dont part it! FABO Gold Member

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        Shell rotella t4 is what my machinist recommended me to run in mine.
         
      • valiantwagonguy

        valiantwagonguy Well-Known Member

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        I use Valvoline VR1 10w 30 racing oil in my 170 slant.It has lots ZINK ! you need zink for the solid lifters and the cam and most modern oil is lacking in zink because modern stuff doesn't need it.
         
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        • slantsixdan

          slantsixdan =..=

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          Short version:

          Use a reputable off-the-shelf brand of engine oil. Avoid making the common error of thinking heavier-weight oil gives better protection—it does not. Using the lightest viscosity grade your engine's mechanical condition and your ambient temperatures will support will ensure quick lubrication of all parts at engine startup, thus reducing wear. For a Slant-6 engine in basically sound condition, 10W-30 is usually a fine choice. For a recently-built engine and/or use in cold weather, 5W-30. For a worn-out engine you're trying to squeeze a few last miles out of, 15W-40 or 20W-50 or straight 30- or 40-weight. Continue using good quality filters (Wix and Purolator are two good brands). When you get a chance, service the oil pressure relief valve to make sure it's doing its job, as described in these two threads: thread 1, thread 2. Avoid the temptation to put additives or "supplements" in your crankcase—at best they do nothing; at worst they do damage and harm, so just use unadulterated oil. Change the oil and filter at a reasonable and appropriate interval (3,000 miles is way too short; it's a foolish waste of money and resources). And…that's it! Pick one of the many other things that are much more worth worrying about. If you want to get educated and know WTF you're talking about on the subject of engine oil for old cars, read this.

          Longer, ranty version:

          Science is wonderful, but it has its limits. For example, it stands absolutely zero chance when pitted against mythology handed down through generations from father to son and baked to impenetrable hardness by endless repetition as "common knowledge" in forums on the internet. Everybody knows your old engine will grind itself to death unless you add this additive (no, wait, that additive! No, you're both wrong, it's this other additive!) to your oil, or always only ever use this specially-formulated oil (no, no, not that one, you gotta get this expensive stuff from a special "dealer!") because the big bad government made the oil companies take out (no, wait, it was GM! No, it wasn't, it was the API! You're both wrong, it was Honda!) the zinc (no, dummy, it's the phosphorus! Shut up, you're both wrong again, it's ZDDP!).

          Never mind that zinc antiwear additives are still present in current regular motor oil, but yesterday's very high levels have been functionally replaced by other chemistry that does at least as good a job.

          Never mind that the current API engine oil tests really, truly, actually do include flat-tappet engines (two different ones!).

          Never mind that the sudden surge in tappet failures within recent memory is directly attributable to the sudden and near-complete outsourcing to China of a giant swath of aftermarket lifters.

          None of that matters, because everyone with an internet connection is a qualified tribologist and petrochemist.

          In the vehicle lighting technical standards and specification world where I live professionally, we have our list of myths and half-understood bits of information that we roll our eyes about people swearing it's gospel truth right out of the Bible.

          The oil people have the same tribulation: the general public reads a well-intentioned but out-of-date, incomplete, and oversimplified article, think they've understood that they have to use a high-ZDDP (zinc/phosphorus) oil in their old car, and then go shouting it all over the internet, whereupon someone else goes "Hey, yeah, I read the same thing!" and the myth gets amplified.

          The evolution of engine oil antiwear chemistry did not start or end with Zinc, Phosphorus, or ZDDP. Don't worry/be happy about it unless worrying makes you happy, in which case don't be happy…worry!

          Some people get a warm fuzzy by paying $10 for a quart of fancy-brand oil and pouring it into a car that doesn't need it…fine, if that makes their socks roll up and down; life is short and people should do what makes them happy.

          For vastly most of us, there is no sound reason, need, or benefit to seeking and paying for specialty boutique oils. The lowest-performing oil on the shelf today is light-years ahead of the best-performing oil on the shelf when the Slant-6 was in production.
           
          Last edited: Aug 31, 2020
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          • ir3333

            ir3333 Well-Known Member

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            5W30 Penzoil or any Dino oil with a regular Fram filter. Change it when it looks dirty.For my fair weather 340 Dart i've gone as long as 3 years. For my daily drivers 10-12000 Km.
             
          • ch1ll

            ch1ll FABO Gold Member FABO Gold Member

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            SSDAN that is damn deep article. I drowned a few pages in.

            I know this.
            I thought Amsoil and its extended drain oils were snake oil.
            But I took chance and still didn't trust them. After filling my crankcase with their oil and one of their filters which is made by Wix to their specifications by the way, I had it tested by an independent oil lab, repeatedly. It went 18,000 miles before the lab recommended changing it. This was in a 2 litre 4 cylinder puddle jumper driven in Wisconsin weather and heat cycling is murder on oil. If I hadn't hit a deer and totaled the car with 225,000 mi on it in 2018, I would still be driving it today. Absolutely no oil related issues at all, car only required scheduled maintenance.
             
          • RustyRatRod

            RustyRatRod Bla de blizhibliz de blatde blizi bla bla FABO Gold Member

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            I use Lucas Hot Rod Oil. 10w30. I like it because it already has a high level of ZDDP mixed in. No need for additives.
             
          • Ottmundr

            Ottmundr 68 Fastback

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            Royal Purple HPS 10-w40
             
          • Slantsix64

            Slantsix64 Well-Known Member

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            Wix filter Oriellys 20w50
             
          • Dartvader440gt

            Dartvader440gt Well-Known Member

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            I'm on the kick that regular off the shelf oil today is better than any oil made when these cars were new. Simple 10-30 and stp or fram filter every 3000 miles. Good to go.
             
          • KosmicKuda

            KosmicKuda FABO Gold Member FABO Gold Member

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            Oh, it's that time again. LOL.

            I make it to the Summit store a couple times a year and usually pick up a 5 qt jug of Lucas 10W-30 Hot Rod Oil. (Note High Zinc on the label) Wix or Purolator filters, NAPA Gold too. Never Fram anymore since the 80s after the guy posted his filter study on EEK.
            I have 8000 miles on my 100% rebuilt 225 and will spend a few extra bucks to ensure reliability. I guess I'm averaging about 2000 miles a year and change it once a year. Winter promotes condensation in my unheated garage so it's not just about mileage.

            The slant 6 has a stand pipe that ensures instant oil at start up.

            I split my driving season between 2 old cars and an 87 Jeep. The 68 will soon be G3 powered so one less car to worry about wiped cams.

            20200901_090133.jpg
             
          • pishta

            pishta I know I'm right....

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            There is an oil refined from natural gas now (Quaker State?) , wonder how good it is. Probably very pure and they have to add a lot of additives to make it API. Walmart bulk buy 10W30 here. Passes the test.
             
          • trapster

            trapster Well-Known Member

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            I use shell rotella T6 15w40. cheap at walmart and synthetic with zinc.
             
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            • slantsixdan

              slantsixdan =..=

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              Here's a nice "money quote" from it:
              The addition of extra ZDDP usually results in reduced cleanliness, higher engine temperatures and more deposits. Some studies have shown that going past 1400 ppm of phosphorus will increase wear over the long term, and going above 2000 ppm will begin to break down iron and result in camshaft spalling.

              I believe you. And I did exactly the same thing with exactly the same results using regular ol' normal ol' boring ol' a-third-of-the-price-of-Scamsoil-ol' synthetic Pennzoil on sale from the parts store.
               
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              • Charrlie_S

                Charrlie_S Well-Known Member

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                I have been using 10-30 API rated "off the shelf" oil in all my cars for the last 20 plus years. From a 86 Toyota pu with over 400,000 miles, to my slant six race cars running turbo's and nitrous, and turning between 6-7,000 RPM. I have never had an oil related engine failure.
                 
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                • Kent mosby

                  Kent mosby FABO Gold Member FABO Gold Member

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                  After studying the 38 pages for hours, I am looking at Royal Purple Duralec Ultra 10-30. DURALEC® ULTRA™ | Royal Purple
                  It is a CI-4/SL 10-30 oil that is good for gas or diesel engines and is zinc fortified. I cannot find out exactly how much Zinc is present but the CI-4 rating usually is nominally about 1350 ppm. This seems to check all the boxes and is readily available and reasonably priced. Thoughts???? BTW, this is for a RB stroker that is only about 500 miles old. @slantsixdan ??
                   
                • ir3333

                  ir3333 Well-Known Member

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                  Do you guys still think we need lots of zinc or are we being duped?
                  Zinc is probably a multi million dollar industry now.
                   
                • KosmicKuda

                  KosmicKuda FABO Gold Member FABO Gold Member

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                  I personally know guys that have wiped cam lobes in their Mopars. Not fun.
                  Last cam i installed was when I helped a young guy install a Comp cam in his Ford 351. Comp stated right up front that the warranty was void unless you used their break-in oil. So we did.
                  There is no doubt that modern oils are formulated with less zinc.
                  Like the old commercial said, "you can pay me now or pay me later."
                  Your choice but I don't want to chance it. I remember the days when I could get a Fram filter and 5 qts of Valvoline for 5 bucks.
                   
                • ir3333

                  ir3333 Well-Known Member

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                  i've posted this before...it makes me wonder?
                   
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                  • briwill70

                    briwill70 Well-Known Member

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                    I'm running basic Castro 10-30 in my slant. 50psi most of the time unless It's hot, in gear at a stop light, then it drops to 25psi.
                     
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