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    Straight weight, straight talk-gctid391713

    Yes, I searched first. Flame throwers on safety please. I have the 1987 GM 305's and have always been confused by the call for 30w straight weight oil. I assume having a 10w-30 or 15w-40 would protect better when starting cold, point being a lighter weight oil gets pumped up easier and faster. I realize that with many oil related questions it often comes down to opinion; for example I do not believe there is scientific evidence that proves sythentic oil protects engines better. If anyone has good (hopefully backed by science) advice to share, it's oil change time for Personal Space. What oil is best - not brand but weight please. Also, I just picked up a "MityVac" oil extractor and I simply can't weight to use it. Man, I crack myself up.

    #2
    "Straight 30W" is just that. Oil the holds it's viscosity throughout it's operating spec.

    Multiple viscosity oils have polymers added to lower weight oil (cheaper oil too) that unwind as the oil heats and make it act thicker. In a perfect world 5W-30 will act just like 30W at temps.

    The problem is we seldom get to those temps reliably in boats and the work in a harsher world causing the polymers to break down.

    I use straight 30W... no need for efficiencies earned with multi-vis oils on my boat.
    Custom CNC Design And Dash Panels

    iBoatNW

    1980 CHB Europa 42 Trawler- "Honey Badger"

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      #3
      The real need for multiviscosiy oil is when you run in really cold temps like winter.

      The newer engines also run at tighter tolerances then those of old so the need for thinner oil upon start up is necessary. If its a new engine I would go 10-30 other wise 30w if you only run in summer
      1989 Avanti 3450 Sunbridge
      twin 454's
      MV Mar-Y-Sol
      1979 Bayliner Conquest 3150 hardtop ocean express.
      Twin chevy 350's inboard
      Ben- Jamin
      spokane Washington

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        #4
        I use 10-30 dino oil, or 5-40 rotella syn.

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          #5
          I don't think there's any question that synthetic performs better, whether you want to pay the difference for that performance is your decision.

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            #6
            A great place to expand your knowledge of oil is BITOG:

            http://www.bobistheoilguy.com/

            Click on "oil forums" at the top to the page and let the info download begin......

            Comment


              #7
              orca wrote:
              I use 10-30 dino oil, or 5-40 rotella syn.
              This debate can go on forever, but I would be hesitant to run a 5W anything in an older small block Chevy. Like was said, these new thinner oils are desinged for new engines with extremely tight tolerances, which an 80's era Small block Chevy is not one of. (My Acura, Yes!) I would run a 10W or even a 20W multi, or a straight 30W.

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                #8
                Actually most new cars 5-30 is recommended. I am leaving out VW's and a few others. What i recommend is what is listed for use on your engine.

                I use straight 30 weight in my 85' 3.0 / 140 hp engine that is in my boat.
                Be good, be happy, for tomorrow is promised to no man !

                1994 2452, 5.0l, Alpha gen. 2 drive. Sold ! Sold ! Sold !

                '86 / 19' Citation cuddy, Merc. 3.0L / 140 hp 86' , stringer drive. Sold ! Sold ! Sold !

                Manalapan N.J

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                  #9
                  My 4-cylinder Volvo calls for 10w-40. I've used 20w-50 and 30w and had 80psi on startup when it was cold out.

                  The manual should have a range of weights to use for the temperature of your area, along with a recommended oil pressure. Adjust weights accordingly.

                  Comment


                    #10
                    iceclimber wrote:
                    Yes, I searched first. Flame throwers on safety please. I have the 1987 GM 305's and have always been confused by the call for 30w straight weight oil. I assume having a 10w-30 or 15w-40 would protect better when starting cold, point being a lighter weight oil gets pumped up easier and faster. I realize that with many oil related questions it often comes down to opinion; for example I do not believe there is scientific evidence that proves sythentic oil protects engines better. If anyone has good (hopefully backed by science) advice to share, it's oil change time for Personal Space. What oil is best - not brand but weight please. Also, I just picked up a "MityVac" oil extractor and I simply can't weight to use it. Man, I crack myself up.
                    Synthetic oil does protect an engine better and there is scientific evidence to prove it. You can't burn synthetic and so there is no possibility of varnishing. I have fixed sticky/ticking lifter problems by doing a single oil change from dino to synthetic.

                    Comment


                      #11
                      Fish-a-Palooza wrote:
                      Synthetic oil does protect an engine better and there is scientific evidence to prove it. You can't burn synthetic and so there is no possibility of varnishing. I have fixed sticky/ticking lifter problems by doing a single oil change from dino to synthetic.
                      Love to see the evidence if you have a link.

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                        #12
                        Pau Hana wrote:
                        A great place to expand your knowledge of oil is BITOG:

                        http://www.bobistheoilguy.com/

                        Click on "oil forums" at the top to the page and let the info download begin......
                        Thanks Pete, I've seen that. My thing is I grew up with the wonders of multi oil and had literally never heard of 30 single grade until I read the manual. I will probably stick with a 10-30 or 30w, and follow the best practice of all. Change your oil often and before winterizing.

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                          #13
                          Synthetic will burn- it'll take much higher temps to do so, but it will burn. One of the chief benefit of synth is that its molecular structure holds together under heat and pressure much better that dino.

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                            #14
                            I run the blend in my car, but only because I change my own and it's a few more bucks. The lube and goob people want like WAY too much money for that.

                            Comment


                              #15
                              I use what the mfg says to use. In my case, it's 20-40 dino. Merc started allowing full synthetic back around mid-90s I think. They also allow single weights based on the surrounding temps, not the operating temp.

                              Single weight oils have one advantage, they shed heat better than multi-vis. Many boats have an inline oil cooler, so heat shedding is not an issue. I haven't seen any benefits to synth oils that would make me spend the extra money for them. I've got two Dodge engines that have over 200k each, and a Ford Diesel > 300k with normal dino oil with regular changes.

                              In my airplane, where the engine was designed by Archimedes, they spec single weight and that's what I run. No synth, no multi-vis, only thing I change from the old oil is a detergent to scrub the insides and deposit the gunk in the after-market installed oil filter. If I didn't have a filter I would be using non-detergent.

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