slant 6 oil weight

Slant 6 Engines

  1. beebeeri000

    beebeeri000 Rest-O-Moder

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    ok so this might sound stupid, but what weight should i put in a high mileage slant 6? chiltons says 10w 30 / 10w 40 where its regularly above 32, but the guy at costless said for a 70's engine it needs straight 30 oil. so im not sure what to use and i dont want to accidentally damage my engine.
     
  2. RustyRatRod

    RustyRatRod Weenie idiot loser. FABO Gold Member

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    Motor oil weighs around 2 pounds per quart. SO that means the slant will hold between 10-12 pounds of oil.
     
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    • beebeeri000

      beebeeri000 Rest-O-Moder

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      i meant oil viscosity some people call it weight
       
    • BillGrissom

      BillGrissom Well-Known Member

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      It is not much different than any modern engine. Indeed, the 3.8L in my 2002 T&C looks very similar to my 60's V-8's (same pushrods, timing chains), so most oils would work. Our flat tappet lifters need as high a zinc content as you can get. I recall some diesel oils (CJ rating) have that. Search since people have talked about that, plus additives. Diesel oil is good to better suspend the black carbon, if your engine is worn (high detergent). A thicker oil will help seal leaking rings. There are "high mileage" oils in the store. For best mileage, a thinner oil helps, even the new 0W20 synthetic.
       
    • RustyRatRod

      RustyRatRod Weenie idiot loser. FABO Gold Member

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      I know. LOL
       
    • nm9stheham

      nm9stheham Well-Known Member

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      IMO... the need for high zinc oils for a stock cam is not necessary. I good lubricating oil is the best for you. And the lifters in the /6 are pretty hard.

      With an older engine and oil pump. the pump may be worn and will have a harder time pulling up a heavier oil. So I would stick with no heavier than 10W30 and consider a 5W20 for your /6.

      The way zinc works, having an excess does nothing unless you run your oil forever and ever. I would strongly suggest anyone wanting to learn more about oil and zinc read this and for the OP to select one of the higher ranked oils in this list. It shows how some zinc additive packages actually reduce the lubricating properties of many oils. This is a long read so be prepared to sit for a while:

      https://540ratblog.wordpress.com/2013/06/20/motor-oil-wear-test-ranking/
       
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      • YoungDart75

        YoungDart75 Well-Known Member

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        I'm running Castrol High Mileage 10w40 in mine and its got 75,000 miles on it here in Great Lakes, Illinois.
         
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        • sargentrs

          sargentrs Well-Known Member

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          Been running store brand 10w30 till I got the kinks worked out.Now that she's running well, changed it and used Valvoline Max Life 10w40. Oil pressure went up 5psi at startup and holds at 40+ cruising and 10+ at idle. Before she'd be lucky to hold 35psi at cruising and 5 at idle. Valves need adjusting but runs quieter too. She definetly like the heavier, higher grade oil. Lot of miles on her so I don't expect much.
           
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          • roccodart440

            roccodart440 Well-Known Member

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            Run the weight that produces the oil pressure you need. I run 0w-40 Mobil One. I only run Mobil 1. I only run full synthetic in all my engines.

            In regards to Zinc. Don't pretend to be a chemist. Buy an oil that has the proper lubrication for your engine.
             
          • pishta

            pishta I know I'm right....

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            dino oil is best to break a motor in, then synthetic. Practically no sludge with synthetic, good stuff.

            Oil depends on climate. So.Cal can run straight 30 but why? multiweight is easiest on pump. ITs like this: 10W40 is 10 at startup (thin, perfect to get the oil to the bearings the fastest) and 40 (gooey) at 100C`(212F) or normal operating temperature, nice and thick like older high mileage cars like with their looser bearing tolerances. you can run 0W30 if you want. its still 30W at operating temp. 0W20 is used nowadays to extract the most mileage of new motors. Modern Science at work.
             
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            • Aaron65

              Aaron65 Well-Known Member

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              Wow...that website is an eye opener! Thanks for posting it!
               
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              • 66fs

                66fs Well-Known Member

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                The Chrysler and Chevrolet Racing manuals said straight 30w oil will result in the least wear. There is no reason to run synthetic oil. Synthetic oil may cause your seals to leak. Old school said, use good oil, change it and the filter every 3,000 miles. You will never have an oil related problem unless you do something stupid. 10w 30 is OK. If you are using excessive oil, try 20-50. I do not like light oil, all the talk about heavy oil is much a do about nothing in my experience. And I have a lot of experience. You are not stupid, it is a overcomplicated subject. Now watch what happens...
                 
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                • roccodart440

                  roccodart440 Well-Known Member

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                  It's not about what you like, it's about what you need. Not every engine needs the same oil. That's why they make many variations of oil. I use light oil (0w-40) because of the pressure my car makes. My last car ran 20w50.

                  If you want to see the benefit of light oil switch from 15w40 to 5w40 in a 7.3l or 6.0l diesel in colder weather.

                  If you want to see the benefit of heavier oil switch from 20w50 to 0w in a full grooved main bearing engine or something with loose tolerances.
                   
                • nm9stheham

                  nm9stheham Well-Known Member

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                  Amen to the lighter oil in the 7.3L and 6.0L in winter!

                  Can't explain the 'don't use synthetic due to leaks' in this day and age. When Mobil 1 first came out in the 70's, only lighter weights were produced and older engines did have some leaks. But the newer variety of synthetic weights has fixed that; it is just 40+ years old old experience hanging on.

                  I run almost 100% synthetics in gas and racing engines but use dino oils in my 2 diesel trucks and just change it a lot. The protection that synthetics offer if something happens in the engine to drop pressure is very real. But it is not for everyone if you are on a budget (though the cost difference has gone down) or are working on the engine.
                   
                • roccodart440

                  roccodart440 Well-Known Member

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                  If you are running synthetics and changing your oil as often as you would with dino oil you are wasting your money. Even in the fords with the HPOP you can go longer on an oil change with full syn and let's face it. They hold 4 gallons of oil. That's really where the money makes sense. Full syn, pay more up front, less changes. DIno oil is cheap but breaks down faster. My dart gets a change once per year no matter what.
                   
                • 66fs

                  66fs Well-Known Member

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                  And yet it still works, and for a lot cheaper. Why do you think newer engines use Viton seal material if neoprene would seal synthetics? I've tried synthetic oil and see no benefit in my old or new cars. Spend all the money you want and tell yourself it is better.
                   
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                  • roccodart440

                    roccodart440 Well-Known Member

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                    My engine doesn't leak. (440)

                    I don't tell myself synthetic is better. I read. Although I am a right wing moderate I do believe in science and math. It is impossible to argue that high end synthetics don't offer better protection. It boils down to choice. I don't care what you use. It isn't my money. I do care if anyone provides false information that will negatively affect other people.
                     
                  • 66fs

                    66fs Well-Known Member

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                    No one is providing false information. Millions of miles in all climates from South Dakota to Miami Florida. High performance to grocery getters. Believe what you read. I do not care. I don't waste money on synthetics. You can, I don't care. I doubt it will harm your engine, unless you go too light. The guy with a 70's slant six does not need synthetic oil let alone light weight oil. As far as being proven, it has not. All the manufacturers and their race teams have stated it is not better. If you think you need it to sleep better at night, and can afford, it go for it. I can afford it and don't use it, you can draw your own conclusions. Every engine I have rebuilt and every car I bought new has at least 250 thousand miles and still runs like new. All with good, "proven inferior oil". Give me a break!
                     
                  • roccodart440

                    roccodart440 Well-Known Member

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                    I never said he needed lightweight oil.
                    I never said he needed synthetic oil.


                    I said to use the weight oil that provides the pressure he needs.
                    I said that I use synthetic in everything I own and that Mobil 1 is my choice.
                    I said do not play chemist. Buy an oil with the proper lubricating properties.


                    :violent2:
                     
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                    • 66fs

                      66fs Well-Known Member

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                      Oh, That's very different, never mind. (in my best Gilda Radner voice.) I caught the "provides false information that will negatively affect other people. " and took offence. Sorry.
                       
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                      • nm9stheham

                        nm9stheham Well-Known Member

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                        I have raced for over 30 years. I had an incident where the oil system leaked all the oil out. I raced 2.5 minutes with falling oil pressure and 2.5 minutes with ZERO oil pressure on Mobil 1 synthetic with a turbo'd engine loaded at over 1.5 HP per cubic inch. Engine never hiccuped or knocked. Tore it down after, and there were NO scratches or wear on the bearings, or rings, or pistons or anywhere. Nothing; looked like I had just assembled and never fired it up. Put it back together and ran it more. No way in hell a dino oil would ever manage that.

                        Before that, I raced for years on good grade dino oil (Castrol GTX). It was always black as could be after a long race. With Mobil 1, it gets a little brown. BIG difference in the break down (oxidation) of synthetic vs dino.

                        That is not 'telling myself it is better; that is real hard knocks experience and actual proof. Gainsay it if you wish but you have no way to know. And the idea that neoprene does not stand up to Mobil 1 is an odd idea for you hold on to, since Mobil 1 is actually a very highly refined petroleum oil. In words originally published by ExxonMobil:

                        "The difference is that synthetic oils [edit to clarify that they mean Mobil 1] undergo numerous additional highly advanced distilling, refining, and purification processes - and therefore are of a higher purity and quality than conventional mineral oils. This not only removes more impurities from the original crude, it also enables the engineering of the lubricant's individual molecules to be uniform and consistent, tailored to meet the specific high-performance demands of modern engines. These customized molecules provide higher levels of protection and performance, even in extreme conditions. "

                        As for the OP's needs: No one said he had to use anything in particular. A number of recommendations and comments were made. A good read of the link I provided is the best info I can point to; it is based on actual film strength testing.
                         
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                        • 75Brougham

                          75Brougham 75Brougham

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                          I run 10w30 in my leaning tower of power (slant six). The W in the oil viscosity code means winter, not weight. Also, the higher the number, the thinner the oil is. So, 10w30 oil will be thicker at start up temps than 5w30, which is what you want for optimum lubrication. The second number, 30, indicates that the oil is thinner at operating temps. Normally in these older engines you run 10w30 or 10w40, however, I would run 10w30 for most sixes and small blocks.
                           
                        • 66fs

                          66fs Well-Known Member

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                          Quite entertaining, but you will not convince me. I have all kinds of stories about running engines without oil and coolant. Way before synthetics were on the market. Racing does not count, you guys don't leave your oil in long enough to get dirty and nasty. I simply have too much experience to believe the marketing. Every one said I'd ruin the engine in my daily driver 96 ACR Neon by running Valvoline Racing 30, 250,000 miles still runs like new. Our 67 273 Barracuda with a Commando 273, 300,000 miles, I can go out after sitting for months it will fire right up. My oil does not get dirty, not that that is an indicator, between changes. We've been running High Performance engines for 40 some years and I've tried most good oils, including Mobil 1 and Amzoil Racing, I see no advantage. I would never run Mobil 1 again. As for running oil without Zinc, most of the good cam manufacturers will not warrantee their cam and lifters without a minimum zinc content. That should tell you something. I don't need a good read. I have yet to have an oil related engine failure and my engines run forever. What is better going to get me, even if it were true???
                           
                        • C130 Chief

                          C130 Chief Mechanical Genius

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                          Be careful using oil pressure to select the appropriate oil viscosity. Keep in mind that viscosity is by definition a liquid's resistance to flow (the weight of motor oil is about 1.7 lb/qt regardless of viscosity), and the oil pressure is measured upstream of all points of demand. So your oil pressure gauge might just be telling you how well the oil isn't doing it's job. An engine with clogged passages could have excellent oil pressure but lubricate poorly. If an engine will not maintain specified pressure with the recommended viscosity the clearances are way out of limits. Thick oil is not a rebuild in a can.

                          10w30 would be perfectly appropriate for a slant. 10w40 would be fine too, especially in warm weather. Synthetic oil IS better, but probably not necessary. Any name brand today is superior to what was available in the late 50's when the engine was designed
                           
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                          • EL5DEMON340

                            EL5DEMON340 Well-Known Member

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                            I would just run valvoline VR1 10/30 as long as you have good oil psi at idle at least 10 at 700rpm. It's high on most of the "lists" plenty of zinc for old flat tappet cams, anti foaming additive for hi rpm, thinner oil cools better especially the valve springs, rockers, bearing and drains back to the pan quicker. The new thinking is to run a hi volume or psi pump with thin racing oil like a 0/20 or 5/30. − 0W-5 for the NHRA Pro Stock, 10W-30 for NASCAR .
                             
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