Info on oil; as stolen from.....a good source
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    Moderator Alan S's Avatar
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    Mar 2001
    Queensland, Australia

    Default Info on oil; as stolen from.....a good source

    We often have long winded discussions of the pros and cons of various oils especially varying types and ratings.
    I have long been a member of the BX16V Club in the UK and the members there in the main are particularly fussy about what they use in their cars when it comes to maintenance as the 16V is becoming a rare beast due to having been thinned out by cannibals taking the engines for other vehicles.
    Below I have done a copy and paste on a couple of articles they have which were written by a member who works for an independent oil company that has been in existence since 1925, so should have a few clues.
    His name and the name of his company and contact details are shown in places and I acknowledge with thanks the effort he has put into the compilation of these articles.
    They are extremely informative and interesting.
    Long read, but worth the effort as it's good information from a reliable source.

    Alan S

    On Synthetics; myth busting:

    As you will probably be able to tell, this was written by a Chemist not a Salesman! It's worth the read though!

    Building a good oil.

    It is impossible to make a good 5w-40 or even 10w-40, using only mineral oil. The base oil is so thin, it just evaporates away at the high temperatures found in a powerful engine that is being used seriously. Although there are chemical compounds in there to prevent oil breakdown by oxygen in the atmosphere (oxidation) they cannot adequately protect vulnerable mineral oil at the 130 degC plus sump temperatures found in a hard working turbocharged or re-mapped engine.

    The answer to this is synthetics. They are built up from simple chemical units, brick by brick so as to speak; to make an architect designed oil with properties to suit the demands of a modern engine.

    The synthetic myth

    The word “synthetic” once meant the brick by brick chemical building of a designer oil but the waters were muddied by a court case that took place in the USA some years ago. The outcome was that the right to call heavily modified mineral oil “synthetic” was won. This was the marketing executives dream; the chance to use the word “synthetic” on a can of oil without spending much extra on the contents!

    Most lower-cost “synthetic” or “semi-synthetic” oils use these “hydrocracked” mineral oils. They do have some advantages, particularly in commercial diesel lubricants but their value in performance engines is marginal.

    TRUE synthetics are expensive and in basic terms there are three broad catagories, each containing many types and viscocity grades:-

    PIB’s (Polyisobutanes)

    These are occasionally used as thickeners in motor oils and gear oils, but their main application is to suppress smoke in two-strokes.

    The TWO important ones are:


    All jet engines are lubricated with synthetic “esters” and have been for more than 50 years but these expensive fluids only started to appear in petrol engine oils around 20 years ago.
    Thanks to their aviation origins, the types suitable for lubricants work well from
    -50 degC to 200 degC, and they have an added benefit. Due to their structure, “ester” molecules are “polar”; they stick to metal surfaces using electrostatic forces. This means that a protective layer is there at all times, even during that crucial start-up period. This helps to protect cams, gears, piston rings and valve train components, where lubrication is “boundary” rather than “hydrodynamic”, i.e. a very thin non pressure-fed film has to hold the surfaces apart.
    Even crank bearings benefit at starts, stops, or when extreme shock loads upset the “hydrodynamic” film.

    Synthetic Hydrocarbons or PAO’s (Poly Alpha Olefins)

    These are, in effect, very precisely made equivalents to the most desirable mineral oil molecules. As with “esters” they work very well at low temperatures and equally well at high temperatures, if protected by anti-oxidants. The difference is, they are inert and not polar. In fact, on their own they are hopeless “boundary” lubricants, with less load carrying ability than a mineral oil. They depend entirely on the correct chemical enhancements.

    It is a fact that “PAO’s” work best in combination with “esters”. The “esters” assist load carrying, reduce friction and cut down seal drag and wear, whilst the “PAO’s” act as solvents for the multigrade polymers and a large assortment of special compounds that act as dispersants, detergents, anti-wear and anti-oxidant agents, and foam suppressants.
    Both are very good at resisting high-temperature evaporation, and the “esters” in particular will never carbonise in turbo bearings even when provoked by anti-lag systems.

    So, in conclusion, Ester gives the best protection and Ester/PAO combinations have great benefits because they work well together. They are more expensive but worth it if you wish to do the best for your engine.

    A question from a member:

    I'll kick off some thoughts from my experience of owning a 16V for getting on 4 years Shocked

    When I first got mine it had a service done and semi-synth put in - at 6k service intervals this seemed OK.

    As it was my new baby and I intend keeping her for some time I opted for fully synthetic at the next service - but by mistake I bought 0W40, which of course escaped every which way Confused

    After a bit of investigation the next oil change was Castrol RS 10W60 fully synthetic - not cheap but Castrol reckoned it was perfectly suited to this engine, particularly as I'm gentle on it from cold....

    Due to a lack of availability I switched to Mobil 1 Motorsport (can't remember the grade, but not 0W?) may be 15W50? This was equally as good, and seemed to require no topping up between services.

    Then my use of the car changed - instead of 6k every 5-6 months I was doing 3k a year, tops! Once I'd used up the stock of Mobil 1 doing annual oil changes (which of course require 2 bottles of oil!!) I swapped back to semi-synth at the last service given that even with annual oil changes rather than 6 monthly the oil was still clean when it was changed and it seemed a bit of a waste of 40+!

    TBH I'm not sure what's in it at the moment - I have the car serviced at a Citroen specialist and asked them to put something 10W or 15W in it, as the manual states. I suspect it's Valvoline, which is also what the Citroen dealer sold me to top up the Xsara VTS we have with a similar engine spec....


    From my point of view fully synthetic is worth paying the extra for if you do a lot of mileage and/or drive the car hard frequently. I haven't tracked mine (yet!) but I don't expect the odd one each year will seriously shorten the life of the oil?



    Well you've certainly tried a few............

    10w-60, I wouldn't use as it's really too thick and, even hot-running engines do not need SAE 60 oil these days. (by ‘hot’ I mean 120-130C). SAE 60 is heavier than most SAE 90 gear oils. If an oil is too thick, it de-aerates slowly, leading to cavitation in the oil pump, or the bearings being fed slugs of air along with the oil.

    10w-40 semi syn seems to be the best bet for these cars unless of course you have a good reason for "stepping out of grade" like 5w-40 fully syn or better cold start protection. 5w circulates better than 10w.

    Hope this helps
    Article on "modding" the engine.

    If you are "modding" your car and adding BHP then consider your oil choice carefully as the stock manufacturers recommended oil will not give you the protection that your engine requires.

    A standard oil will not be thermally stable enough to cope with higher temperatures without "shearing" meaning that the oil will not give the same protection after a couple of thousand miles as it it when it was new.

    Let’s start with the fundamentals. An engine is a device for converting fuel into motive power. Car enthusiasts get so deep into the details they lose sight of this!

    To get more power, an engine must be modified such that it converts more fuel per minute into power than it did in standard form. To produce 6.6 million foot-pounds per minute of power (ie 200 BHP) a modern engine will burn about 0.5 litres of fuel per minute.(Equivalent to 18mpg at 120mph). So, to increase this output to 300BHP or 9.9 million foot-pounds per minute it must be modified to burn (in theory) 0.75 litres.
    However, fuel efficiency often goes out of the window when power is the only consideration, so the true fuel burn will be rather more than 0.75 litres/min.

    That’s the fundamental point, here’s the fundamental problem:

    Less than 30% of the fuel (assuming it’s petrol) is converted to all those foot-pounds. The rest is thrown away as waste heat. True, most of it goes down the exhaust, but over 10% has to be eliminated from the engine internals, and the first line of defence is the oil.

    More power means a bigger heat elimination problem. Every component runs hotter; For instance, piston crowns and rings will be running at 280-300C instead of a more normal 240-260C, so it is essential that the oil films on cylinder walls provide an efficient heat path to the block casting, and finally to the coolant.

    Any breakdown or carbonisation of the oil will restrict the heat transfer area, leading to serious overheating.

    A modern synthetic lubricant based on true temperature-resistant synthetics is essential for long-term reliability. At 250C+, a mineral or hydrocracked mineral oil, particularly a 5W/X or 10W/X grade, is surprisingly volatile, and an oil film around this temperature will be severely depleted by evaporation loss.

    Back in the 1970s the solution was to use a thick oil, typically 20W/50; in the late1980s even 10W/60 grades were used. But in modern very high RPM engines with efficient high-delivery oil pumps thick oils waste power, and impede heat transfer in some situations.

    A light viscosity good synthetic formulated for severe competition use is the logical and intelligent choice for the 21st century.
    You must seriously consider a "true" synthetic for "shear stability" and the right level of protection.

    Petroleum oils tend to have low resistance to “shearing” because petroleum oils are made with light weight basestocks to begin with, they tend to burn off easily in high temperature conditions which causes deposit formation and oil consumption.

    As a result of excessive oil burning and susceptibility to shearing (as well as other factors) petroleum oils must be changed more frequently than synthetics.

    True synthetic oils (PAO’s and Esters) contain basically no waxy contamination to cause crystallization and oil thickening at cold temperatures. In addition, synthetic basestocks do not thin out very much as temperatures increase. So, pour point depressants are unnecessary and higher viscosity basestock fluids can be used which will still meet the "W" requirements for pumpability.

    Hence, little or no VI improver additive would need to be used to meet the sae 30, 40 or 50 classification while still meeting 0W or 5W requirements.

    The end result is that very little shearing occurs within true synthetic oils because they are not "propped up" with viscosity index improvers. There simply is no place to shear back to. In fact, this is easy to prove by just comparing synthetic and petroleum oils of the same grade.

    Of course, the obvious result is that your oil remains "in grade" for a much longer period of time for better engine protection and longer oil life.

    If you would like advice then please feel free to ask.


    Email me : [email protected]
    Tech Info:

    Call me: 01209 215164
    Last edited by Alan S; 9th November 2005 at 09:18 AM.
    If it ain't broke, use a 12" shifter.....that usually does the trick!!

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