Oil – You get what you pay for!

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  • oilman
    S2Forum Maniac
    • Jan 2006
    • 996
    • Country: United Kingdom

    #1

    Oil – You get what you pay for!

    Costs of synthetics vary considerably. The most expensive are the “Ester” types originally only used in jet engines. These cost 6 to 10 times more than high quality mineral oils.

    The cheapest synthetics are not really synthetic at all, they are dug out of the ground and not manmade. These are in fact specially refined light viscosity mineral oils known as “hydrocracked” oils.

    “Hydrocracked” oils have some advantages over their equivalent mineral oils, particularly in lower viscosity motor oils such as 5w-30 and 5w-40 and they cost about 1.5 times more than good quality mineral fractions. This is the “synthetic” which is always used in cheap oils that are labelled “synthetic”.

    So, why are these special mineral oils called “synthetic”?

    Well, it all came about from a legal battle that took place in the USA more than ten years ago. Sound reasons (including evidence from a Nobel Prize winning chemist) were disregarded and the final ruling was that certain mineral bases that had undergone extra chemical treatments could be called “synthetic”.

    Needless to say, the marketing executives wet their knickers with pure delight! They realised that this meant, and still does, that the critical buzz-word “synthetic” could be printed on a can of cheap oil provided that the contents included some “hydrocracked” mineral oil, at a cost of quite literally a few pence.

    So, the chemistry of “synthetics” is complex and so is the politics. The economics are very simple though.

    If you like the look of a smart well-marketed can with “synthetic” printed on it, fair enough, it will not cost you a lot; and now you know why this is the case, it’s really only a highly processed mineral oil.

    But, if you drive a high performance or modified car, and you intend to keep it for several years, and maybe do the odd “track day” or “1/4 mile”, then you need a genuine Ester/PAO (Poly Alpha Olefin) synthetic oil.

    These oils cost more money to buy, because they cost a lot more money to make.

    Very simply, you always get what you pay for, cheap oils contain cheap ingredients, what did you expect!
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  • MidnightBlueS2
    S2Forum Extremist
    • Jul 2005
    • 1653
    • Home: United States Current: Belgium

    #2
    Always good info to read !

    As you're the oil expert here, what's your opinion on Mobil 1 5W-50 please ?
    Midnight Blue S2 - SOLD - 1993 S2 Avant

    Comment

    • Nj
      S2Forum Possessed
      • Jan 2007
      • 3420
      • Home: Scotland Current: Finland

      #3
      damn. that's some educational posting right there. So save me a bit of head scratching - what kind of oil would you recommend for the average s2forum member. 100 to 200 thousand miles on the clock? And are we basically saying the Halfords, Castrol etc Synthetics are crap?
      cheers
      Nj
      --------------------------------------------------------------------
      1990 CQ20v
      2001 3.0 B6 A4 Avant Quattro Sport

      Comment

      • MidnightBlueS2
        S2Forum Extremist
        • Jul 2005
        • 1653
        • Home: United States Current: Belgium

        #4
        Originally posted by fourcircle
        damn. that's some educational posting right there. So save me a bit of head scratching - what kind of oil would you recommend for the average s2forum member. 100 to 200 thousand miles on the clock? And are we basically saying the Halfords, Castrol etc Synthetics are crap?
        cheers
        Nj
        Subject has been extensively debated in other threads... Do a search, there's loads to read.

        A lot of us use Millers 10w-60, Castrol RS 10w-60 ( MRC Tuning recommended ), Motul 10w-50 and Mobil1 5w-50

        Standard recommendation of Audi is 10w-40
        Midnight Blue S2 - SOLD - 1993 S2 Avant

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        • Nj
          S2Forum Possessed
          • Jan 2007
          • 3420
          • Home: Scotland Current: Finland

          #5
          aha. cool. i'll have a nosey at past threads then. cheers for the advice.
          --------------------------------------------------------------------
          1990 CQ20v
          2001 3.0 B6 A4 Avant Quattro Sport

          Comment

          • oilman
            S2Forum Maniac
            • Jan 2006
            • 996
            • Country: United Kingdom

            #6
            Originally posted by MidnightBlueS2
            Always good info to read !

            As you're the oil expert here, what's your opinion on Mobil 1 5W-50 please ?
            We sell Mobil but not this one as we cannot get hold of it.

            5w-50 is a difficult grade to blend due to the anount of VI improvers required to make it work. A 10w-50 or 15w-50 would doubtless be more stable as would a 5w-40.

            Depends what the car is used for and how modded it is as to the suitability.

            Viscosity Index Improvers.

            An oils viscosity will decrease as the engine temperature rises. Viscosity Index Improvers are added to reduce this thinning. They are a key addative in the production of multigrade oils.

            VI Improvers are heat sensitive long chain, high molecular weight polymers that increase the relative viscosity of the oil at high temperatures. They work like springs, coiled at low temperatures and uncoiling at high temperatures. This makes the molecules larger (at high temps) which increases internal resistance within the thinning oil. They in effect "fight back" against the viscosity loss in the oil.

            "Shearing"

            The long chain molecules in VI Improvers are prone to "shearing" with use which reduces their ability to prevent the oil from losing viscosity. This "shearing" occurs when shear stress ruptures the long chain molecules and converts them to shorter, lower weight molecules. The shorter, lower weight molecules offer less resistance to flow and their ability to maintain viscosity is reduced.

            This shearing not only reduces the viscosity of the oil but can cause piston ring sticking (due to deposits), increased oil consumption and increased engine wear.

            Like basestock quality, VI Improvers also vary in quality. The best quality ones are normally found in synthetic oils (Group IV - PAO / Group V - Esters) and it is important to understand that the less of these in the oil the better the oil will stay in grade.

            Which oils require more VI Improvers?

            There are two scenarios where large amounts of these polymers are required as a rule.

            Firstly in "wide viscosity" multigrades. By this I mean that the difference between the lower "W" number and the higher number is large for example 5w-50 (diff 45) and 10w-60 (diff 50) are what is termed as "wide viscosity" oils.

            Narrow viscosity oils like 0w-30 (diff 30) or 5w-40 (diff 35) require far less VI Improvers and therefore are less prone to "shearing".

            Secondly, mineral and hydrocracked (petroleum synthetic oils) require more VI Improvers than proper PAO/Ester (Group IV or V) synthetic oils as they are less thermally stable to begin with and this is due to the non-uniform molecules in petroleum oils as opposed to the uniformity of synthetics built in laboratories by chemists.

            It is a fact that some synthetics require little or no VI Improvers to work as a multigrade due to their superior thermal stability.

            How to identify a good "shear stable" oil.

            API and ACEA both conduct tests called HTHS (High Temperature/ High Shear) and all oils carrying these specifications are tested and scored.

            For all oils, these test results are available however, they are often ommitted from the oils technical data sheet! Oil Companies have a tendency to publish the figures that they want you to see and therefore you often need to dig further or ask for certain information when comparing the performance of various oils.

            High-Temperature/High-Shear

            This test is a simulation of the shearing effects that would occur within an engine. In fact, it's actually designed to simulate motor oil viscosity in operating crankshaft bearings.

            Under high stress conditions where shearing can occur, the VI Improvers (polymers) break down. As they do, the viscosity of the oil decreases. This is what the High Temperature/High Shear test checks for.

            The HT/HS test is measured in Centipoise (cP) as the Cold Crank Simulator test is. However, in this case, because you're hoping for the least loss of viscosity with an increase in heat and stress, you want the cP value to remain high.

            Each SAE multi-viscosity grade has a specific lower limit for the HT/HS cP value. If a multi-viscosity oil cannot achieve a cP value above that limit, it cannot be classified under that viscosity grade. For instance, according to the SAE specifications, an oil must achieve an HT/HS cP value of 3.7 or higher in order to be classified at the 15w40 viscosity grade.

            The thinner the oil the lower the number.

            Comparisons of HTHS numbers.

            Here for comparison sake are a few numbers that we have compiled from data sheets and requests to the oil companies concerned. These are well known oils and considered to be "quality" synthetics so these comparisons are relevant.

            Silkolene PRO S 5w-40
            HTHS 4.07

            Motul 300V 5w-40
            HTHS 4.51

            Silkolene PRO S 10w-50
            HTHS 5.11

            Motul 300V 10w-40
            HTHS 4.19

            Silkolene PRO R 15w-50
            HTHS 5.23

            Motul 300V 15w-50
            HTHS 5.33

            Mobil 1 Motorsport 15w-50
            HTHS 5.11

            Castrol RS 10w-60
            HTHS 3.70

            Cheers
            Simon
            Use the code S2F and get 10% Club Discount
            oilman's website for BMW engine oil and much more - register for news and offers
            email: sales@opieoils.co.uk
            phone: 01209 202944

            Comment

            • oilman
              S2Forum Maniac
              • Jan 2006
              • 996
              • Country: United Kingdom

              #7
              Originally posted by fourcircle
              damn. that's some educational posting right there. So save me a bit of head scratching - what kind of oil would you recommend for the average s2forum member. 100 to 200 thousand miles on the clock? And are we basically saying the Halfords, Castrol etc Synthetics are crap?
              cheers
              Nj
              If the car is standard and driven on the road then what Audi recommends will be fine.

              A 10w-40 semi-synthetic or a 5w-40 synthetic would be my recommendation.

              The proper synthetic issue becomes more relevant when the car is modified or used off road.

              Cheers
              Simon
              Use the code S2F and get 10% Club Discount
              oilman's website for BMW engine oil and much more - register for news and offers
              email: sales@opieoils.co.uk
              phone: 01209 202944

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              • HPmuirt
                S2Forum April Fool
                • Apr 2005
                • 3014
                • Home: United Kingdom Current: England

                #8
                So would I be correct in assuming that since Silkolene PRO S (10w-50), Silkolene PRO R (15w-50) & Motul 300V (15w-50) had the highest HTHS scores, that they are the least likely to break down (or rather, last the longest before breaking down) and therefore are the best oils to use?

                If so, is the HTHS value more important than the upper and lower W grade values, for those of us who live in temperate western European climates?

                Many thanks for the great posts.

                Cheers n

                Si
                95 ABY S2 Coupe - Ragusa Green
                Subtle mods here and there


                2011 A5 3.0 TDi - Lava Grey
                With every option available (except a towball)

                Comment

                • Nj
                  S2Forum Possessed
                  • Jan 2007
                  • 3420
                  • Home: Scotland Current: Finland

                  #9
                  cheers Simon. I'll keep re-reading this post until I can keep some of it in my head to use when the next Halfords chap decides to impart his oily wisdom upon me.
                  --------------------------------------------------------------------
                  1990 CQ20v
                  2001 3.0 B6 A4 Avant Quattro Sport

                  Comment

                  • oilman
                    S2Forum Maniac
                    • Jan 2006
                    • 996
                    • Country: United Kingdom

                    #10
                    Originally posted by HPmuirt
                    So would I be correct in assuming that since Silkolene PRO S (10w-50), Silkolene PRO R (15w-50) & Motul 300V (15w-50) had the highest HTHS scores, that they are the least likely to break down (or rather, last the longest before breaking down) and therefore are the best oils to use?

                    If so, is the HTHS value more important than the upper and lower W grade values, for those of us who live in temperate western European climates?

                    Many thanks for the great posts.

                    Cheers n

                    Si
                    Yes, they are the leat lilkely to break down.

                    But you also need the correct viscoisty too, so I its all about compromise and what is best for you.

                    Cheers

                    Guy.
                    Use the code S2F and get 10% Club Discount
                    oilman's website for BMW engine oil and much more - register for news and offers
                    email: sales@opieoils.co.uk
                    phone: 01209 202944

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                    • HPmuirt
                      S2Forum April Fool
                      • Apr 2005
                      • 3014
                      • Home: United Kingdom Current: England

                      #11
                      Originally posted by oilman
                      Yes, they are the leat lilkely to break down.

                      But you also need the correct viscoisty too, so I its all about compromise and what is best for you.

                      Cheers

                      Guy.
                      Ok thanks.

                      This of course leads to the follow-up question.... In your opinion, what should the following cars use: -

                      Standard S2/RS2 (spirited road use only)
                      Standard S2/RS2 (regularly tracked or 1/4 miled)
                      Modified (say 400+BHP) S2/RS2 (spirited road use only)
                      Modified (say 400+BHP) S2/RS2 (regularly tracked or 1/4 miled)

                      Cheers n

                      Si
                      95 ABY S2 Coupe - Ragusa Green
                      Subtle mods here and there


                      2011 A5 3.0 TDi - Lava Grey
                      With every option available (except a towball)

                      Comment

                      • oilman
                        S2Forum Maniac
                        • Jan 2006
                        • 996
                        • Country: United Kingdom

                        #12
                        Originally posted by HPmuirt
                        Ok thanks.

                        This of course leads to the follow-up question.... In your opinion, what should the following cars use: -

                        Standard S2/RS2 (spirited road use only) = 5w-40
                        Standard S2/RS2 (regularly tracked or 1/4 miled) = 5w-40/10w-50
                        Modified (say 400+BHP) S2/RS2 (spirited road use only) = 10w-50
                        Modified (say 400+BHP) S2/RS2 (regularly tracked or 1/4 miled) = 10w-50

                        Cheers n

                        Si
                        As a guide.

                        Cheers

                        Guy.
                        Use the code S2F and get 10% Club Discount
                        oilman's website for BMW engine oil and much more - register for news and offers
                        email: sales@opieoils.co.uk
                        phone: 01209 202944

                        Comment

                        • HPmuirt
                          S2Forum April Fool
                          • Apr 2005
                          • 3014
                          • Home: United Kingdom Current: England

                          #13
                          Brilliant...thanks for that, I have always worried that I was using the wrong oil. I currently run an unmodified S2 with occasional track days, so my 5w-40 is OK...phew.

                          Cheers n

                          Si
                          95 ABY S2 Coupe - Ragusa Green
                          Subtle mods here and there


                          2011 A5 3.0 TDi - Lava Grey
                          With every option available (except a towball)

                          Comment

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