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  • Oil grades info

    Did you ever wonder which to buy 15W40 or 10W40 or synthetic or not


    Viscosity
    This is simply the most important feature of any lubricating oil. It can be defined as a fluid's resistance to flow. As the temperature of an oil increases its viscosity decreases.
    If an oil is to thin the lubricant film will break down under conditions of high stress. This allows metal to contact metal causing increases in friction, component damage and ultimately equipment failure. If the viscosity of the oil is too high then it is physically unable to squeeze between two metal surfaces.

    The Society of Automotive Engineers Viscosity Classification
    The terms SAE 10W-30 and SAE 15W-40 are widely used. How many people actually understand what these terms mean?
    Firstly any viscosity grade should be proceeded by the initials SAE. This stands for the Society of Automotive Engineers and indicated that the following viscosity classification refers to their definitions. It should be noted that SAE is not a performance category it only refers to the viscosity of the oil. When comparing oils the reader should not only compare the SAE viscosity grades of two oils but also the engine performance classifications in order to be able to fully compare performance.

    Let us consider the following: SAE 15W-40.
    The fact that this classification has two parts; the 15W and the 40 indicates that the oil is a multigrade. The first number with the suffix 'W' indicates the oil's performance at low temperature. In fact the 'W' stands for winter. The lower the 'W' number the lower the viscosity of the oil. Therefore an SAE 5W oil is a lower viscosity oil than an SAE 10W oil.

    The number after the W, in the above case '40'; gives a measure of the oil's viscosity at high temperature. Again the lower the number the thinner the oil is at high temperature. So an SAE 30 is a thinner, or less viscous, oil than an SAE 40.

    A multigrade oil is an oil that has two parts such as SAE 15W-40, or 20W-50. A monograde oil only has one part, such as SAE 30, or SAE 40.

    What is better a SAE 10W-40 or an SAE 15W-40?
    Using the simple rules above it is clear to see that both of these oils have a similar high temperature viscosity as indicated by the '40'. However the 10W-40 is a thinner oil than the SAE 15W-40 at cold temperatures. Simply apply the rule that the lower the 'W'; number the thinner the oil. The SAE 10W is lower than the SAE 15W and hence is a thinner oil. Therefore in cold temperatures we can state that the SAE 10W-40 oil is better than the SAE 15W-40 oil. In winter the end user may experience a benefit by moving from an SAE 15W-40 oil to an SAE 10W-40 oil.

    Can I use an SAE 10W-30 in summer
    During summer when ambient temperatures are high the oil will tend to be thinner so a more viscous oil should be preferred. The SAE 10W-30 is a thin oil so generally speaking either an SAE 10W-40 or SAE 15W-40, both more viscous, could offer better engine protection. In summer is an SAE 10W type oil required? Probably not so the SAE 15W-40 would be the best recommendation. As a first step the manufacturer's recommendations should be followed.
    In winter the situation is reversed and the SAE 10W-30 oil or the SAE 10W-40 should be favoured.

    Mineral Oils Versus Synthetic Oils
    There is much discussion about mineral oils versus synthetic oils and the relative performance of each type. It is clear that synthetic oils offer certain advantages over mineral oils in terms of low temperature performance, and high temperature oxidation stability but that is not the whole story. Synthetic oils are very expensive and properly formulated mineral oils are more than suitable for most engine applications. A synthetic oil can be considered for very cold temperatures, or for application that may need an outstanding level of oxidation protection but it should be remembered there is a significant cost. The question should always be asked: ‘Can I use a properly formulated mineral oil for this application?'


    I got this from a Chevron site (and so that they dont sue let me say Chevron Oils are marvellous and we all love Chevron Oils).
    Makes me laugh knowing the cheaper 10W40 stuff was better in the cold months

  • #2
    The thing to add to this is that although at the start it states that a thinner oil will break down under high stress, in Winter you need a thin oil to aid starting and get round the engine quicker. You will end up with lower indicated oil pressure but better oil distribution than with a thicker oil.

    You have to wigh up the pros and cons of particular oils on different engines and for different situations. For high performance engines a thinner oil is generally preferred as oil pressure builds faster and therefore the oil gets round the engine better. For older engines a thicker multigrade is much preferred like the old 20W 50 grade that we all used to use. It's interesting that on an older engine, a lot of unscrupulous people used to put thicker oil before selling to quieten down the engine so if you ever go to buy an old Ford escort / Fiesta etc and it's got a quiet engine then either someone has put thick oil or an additive in it, or it's got a new engine cos they aren't quiet engines.

    I just changed my oil for Castrol GTD Magnatec 15W 40 and the oil pressure is much reduced from the old dirty oil (as the new stuff is nice and clean and thin, however what oil pressure I get comes up almost instantaneously.

    I used to run a highly modified Mini and used Mobil Sythnthetic oil in it. Oil pressure at max was just over 30PSI but I ran over 15000 miles with that engine and it redlined at 9500 rpm with no bad effects.

    Sorry a bit rambling but good info (I think) all the same.

    Cheers

    Comment


    • #3
      COming from a motorcycling point of view I'd say this as a general rule of thumb as far as synthetic/versus mineral based oils.

      If you can afford it go for the synthetic, it maintains it's structure for a lot longer than mineral based oil, we always recommended it for any kind of sports/big capacity bike. Oil is THE lifeblood of your engine, skimping on it is false economy and change your oil filter at EVERY oil change, it only takes on little piece of muck to block an oil feed and hey presto it's engine re-build time which costs a damn site more than 5 odd litres of good oil and a filter. Just my thoughts
      Life is not a dress rehearsal
      1996 3.0 SSR-G 5-speed
      (Auto's are for the indecisive!!)

      Comment


      • #4
        You simply can't get better than Mobil 1 SAE 0 - 40. Fully synthetic, cost a fortune, lasts forever (well almost) and comes in petrol version or turbo diesel version. £35 for 4 litres
        Nice when clean, better when muddy

        Comment


        • #5
          Originally posted by Gibber
          You simply can't get better than Mobil 1 SAE 0 - 40. Fully synthetic, cost a fortune, lasts forever (well almost) and comes in petrol version or turbo diesel version. £35 for 4 litres
          Generally can't go wrong with Mobil oils full stop. I was recommended to use Mobil 1 at least on my Min by the company that built the engine.

          Cheers

          Comment


          • #6
            The 0W 40 just gets around the engine as soon as you turn the key. It's absolutely brilliant in the cold weather.
            Nice when clean, better when muddy

            Comment


            • #7
              I hope most people took from the top article the fact that they shouldnt be wasting their money on oils which are top of the range because their engines dont need it. Most people will never own a high performance car and the surf isnt one.

              In Tony's spec thread re Toyota oil spec for the surf, the recommended is and American standard API - C.

              I bought cheaper oil 'Carlube' Turbo Diesel Oil 15W40 for €15 approx £10 and that was for 5 ltrs not for the new 4.5 ltr can they are all going for. It well exceeds the API standard. It also well exceeds the European standard ACEA and according to them is suitable for high-performance diesels and direct injection diesels with long service intervals. The old oil names will always have a recognisable brandname and expect me to pay more for it but shag the name.

              Comment


              • #8
                i'll have to print that off... i've argued with my mate for ages that the W stands for winter... he reckons it's weight.

                just for the record i put in 10W40 magnatec this time, but for the summer i use the free stuff you get with the truck at work!
                i do find that it takes a couple of seconds for the oil light to go out with the 10W40 though?? is this because it's thinner and drains to the sump overnight?
                nee nar nee nar, i'm a fire engine!

                Comment


                • #9
                  Yes the oil does drain to the sump overnight and probably 'a couple of seconds' for the oil light to go out is OK(on a bike you'd only see that delay at oil/filter change which is where my mechanical experience lies) as it's a big ole engine, however much more than 2 seconds and I'd say you have a problem either with your oil pressure full stop(worn big ends anyone?)or the oil pump/oil filter/sump oil strainer take your pick but I wouldn't worry about it too much.................feeling paranoid about it yet? he he he This IS just my opinion and others may disagree but an engine is an engine and generally suffer the same kind of issues it's just the degree of expense and chaos that varies!
                  Life is not a dress rehearsal
                  1996 3.0 SSR-G 5-speed
                  (Auto's are for the indecisive!!)

                  Comment


                  • #10
                    Originally posted by Pete The Tart
                    Yes the oil does drain to the sump overnight and probably 'a couple of seconds' for the oil light to go out is OK(on a bike you'd only see that delay at oil/filter change which is where my mechanical experience lies) as it's a big ole engine, however much more than 2 seconds and I'd say you have a problem either with your oil pressure full stop(worn big ends anyone?)or the oil pump/oil filter/sump oil strainer take your pick but I wouldn't worry about it too much.................feeling paranoid about it yet? he he he This IS just my opinion and others may disagree but an engine is an engine and generally suffer the same kind of issues it's just the degree of expense and chaos that varies!
                    On mine as I said in my first post, I actually get oil pressure quicker with thinner oil than with thicker oil, however overall the actuall pressure is lower.

                    Cheers

                    Comment


                    • #11
                      Originally posted by lucky
                      On mine as I said in my first post, I actually get oil pressure quicker with thinner oil than with thicker oil, however overall the actuall pressure is lower.

                      Cheers
                      it always happens on trucks, then just give it a little rev and the light goes out... just didn't happen on the surf until i changed the oil!... i'm not worried, it doesn't make any nasty rattly cam noises on start, so it should be ok!
                      nee nar nee nar, i'm a fire engine!

                      Comment


                      • #12
                        disconnect a couple of glow plugs, the extra cranking before it starts will circulate the oil around the motor.

                        4x4toys.co.uk - Keeping you on and off the road...

                        Comment


                        • #13
                          Phew!

                          Sorry glazed over reading that!

                          Will come back to it when there are no distractions!
                          I love her, but she keeps on taking!

                          Comment


                          • #14
                            Sorry

                            Sorry! Glazed over. Wrong time o night to have read your thread. Will come back to it 2moro, early evening! From what I could tell tho worth reading.
                            I love her, but she keeps on taking!

                            Comment


                            • #15
                              Wow! 2 totally pointless replies (3 now) to a 5 and a half year old thread...
                              Do you know that, with a 50 character limit, it's

                              Comment

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