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Read our primer articles on High Mileage Oil, Synthetic Oil and Kinematic Viscosity

The Author is John Rowland (Chief R&D Chemist for Silkolene/Fuchs) and it was originally called "Lubricating a Subaru" but don't let that put you off, it applies to any performance car on or off road. ENJOY!

Basically

Basically, to use that irritating in-word, engine lubrication is simple, and consequently boring. So I intend to treat the subject “complicatedly”, which may not be an in-word, but makes life far more interesting!

So, to take a quick look at the simple picture; the oil keeps moving parts apart, reducing friction and carrying away heat. Where there is metal-to-metal contact there are chemicals in the oil to reduce damage. Because the internal combustion process is always less than perfect, some soot is produced and this must be washed off the pistons and rings by the oil, so it has a cleaning or detergent function as well.

The trouble is, all this is just as true for Henry Ford’s original Model T engine as it is for the Subaru or any other high output motor. So where is the difference? The Model T, with 10bhp/litre at 2,000rpm and a single underhead camshaft, was filled with a thick, greenish liquid from somewhere near the bottom of the distillation colums on the Pennsylvania oilfields. It did a vague tour of the internals by guesswork (there was no oil pump) at a temperature around 50 degC, and lasted for 1,000 miles. On the plus side, some of the impurities acted as anti-wear and detergent chemicals. They didn’t work very well, but it was better than nothing. The engine wore out in around 20,000 miles, but even ordinary people, not just amateur rally drivers, were happy to put up with this.

The difference begins with the first turn of the key. The modern high-pressure pump would cavitate on the old heavy monogrades, starving the bearings for a vital couple of seconds, even in warm weather. Likewise, cam lobes would suffer as the sluggish oil found its way along narrow oil ways to the valve gear. The turbo bearing (if fitted as the handbooks say) already spinning fast, would also starve, and when it got going, how long would it be before the heat soak-back fried the primitive oil into a lump of carbon? (This was the problem with “modern” oils only 15 years ago).

So, a good oil must be quite low in viscosity even in the cold, so that it gets around the engine in a fraction of a second on start-up. On the other hand, it must protect engine components (piston rings for example) at temperatures up to 300 degC without evaporating or carbonising, and maintain oil pressure.

Unmodified thin oils simply can’t manage this balancing act. The answer is to use a mixture of thin oil and temperature-sensitive polymer, so as the thin oil gets even thinner with increasing temperatures as the engine warms up, the polymer expands and fights back, keeping the viscosity at a reasonable level to hold oil pressure and film thickness on the bearings. This is called a multigrade.

But, this is all too basic! What I have just written was and is relevant to a 1958 Morris Minor.

The questions that performance car owners need to ask are: “Will this thin oil evaporate and be drawn into the intake manifold (via the closed circuit crankcase ventilation), leading to combustion chamber deposits and de-activated catalysts?” and “Will the polymer shear down at high engine revolutions and high temperatures, causing low oil pressure and component wear?” and “Will it carbonise on the turbo bearing?” These are 21st century questions which cannot be answered by a basic 1990’s approach.

BUT! Before we head into more complications, some figures………

The SAE Business (American Society of Automotive Engineers)

Viscosity is the force required to shear the oil at a certain speed and temperature. Oils work because they have viscosity; the drag of a rotating part pulls oil from a low-pressure area into a high pressure area and “floats” the surfaces apart. This is called “hydrodynamic lubrication”, and crank bearings depend on it. In fact a plain bearing running properly shows literally no metal-to-metal contact. Experimental set-ups have shown that electrical current will not flow from a crank main bearing to the shells. Also, the energy loss due to friction (the co-efficient of friction) is incredibly low, around 0.001. So for every kilogram pulling one way, friction fights back with one gram. This is very much better than any “dry” situation. For example, the much over-rated plastic PTFE has a co-efficient of friction on steel of 0.1, 100 times worse than oil.

Oil viscosities are accurately measured in units called “Centistokes” at exactly 100 degC. These fall into five high temperature SAE catagories:-

SAE No. 20 30 40 50 60
Viscosity Range 5.6 - <9.3 9.3 - <12.5 12.5 - <16.3 16.3 - <21.9 21.9 - <26

A decent quality oil usually has a viscosity that falls in the middle of the spec, so a SAE 40 will be about 14 Centistoke units, but SAE ratings are quite wide, so it’s possible for one 40 oil to be noticeably thicker or thinner than another.

When the polymer modified multigrades appeared, a low temperature range of tests were brought in, called “W” for winter (it doesn’t mean weight). These simulate cold starta at different non-ferrous monkey endangering temperatures from –15 degC for the 20w test to a desperate –35 degC for 0w. So, for example, an SAE 5w-40 oil is one that has a viscosity of less than 6600 units at –30 degC, and a viscosity of about 14 units at 100 degC.

Now, those of you who have been paying attention will say “Just a minute! I thought you said these multigrade polymers stopped the oil thinning down, but 6600 to 14 looks like a lot of thinning to me!”. Good point, but the oil does flow enough to allow a marginal start at –30 degC, and 14 is plenty of viscosity when the engine is running normally. (A lot more could damage the engine. Nobody uses the 24 viscosity SAE 60 oils any more.) The vital point is, a monograde 40 would be just like candle wax at –30 degC, and not much better at –10 degC. It would even give the starter motor a fairly difficult time at 0 degC. (At 0 degC, a 5w-40 has a viscosity of 800 but the monograde 40 is up at 3200!)

Another basic point about wide ranging multigrades such as 5w-40 or 0w-40 is that they save fuel at cruising speeds, and release more power at full throttle. But complications arise……..

Building a good oil

A cave may not be the best place to live, but it’s ready-made and cheap. This is the estate agent’s equivalent of an old style monograde oil. Or you could get Hengist Pod to fit a window and a door; this is moving up to a cheap and cheerful mineral 20w-50. But an architect-designed “machine for living in”, built up brick by brick, is an allegory of a high performance synthetic 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 hard worked turbocharged or re-mapped engines.

Synthetics are the answer. 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 modern engine.

But sometimes, if you look behind the façade, there is a nurky old cave at the back! This is because the marketing men have been meddling!

The Synthetic Myth

What do we mean by the word “synthetic”? Once, it meant the “brick by brick” chemical building of a designer oil, but the waters have been muddied by a court case that took place in the USA a few years ago, where the right to call heavily-modified mineral oil “synthetic”, was won. This was the answer to the ad-man’s dream; the chance to use that sexy word “synthetic” on the can….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 (about 6 times more than top quality mineral oils). Looked at non-basically there are three broad catagories, each containing dozens of types and viscosity 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 2-strokes.

The two important ones are:

Esters

All jet engines are lubricated with synthetic esters, and have been for 50 years, but these expensive fluids only started to appear in petrol engine oils about 20 years ago. Thanks to their aviation origins, the types suitable for lubricants (esters also appear in perfumes; they are different!) work well from –50 degC to 200 degC, and they have a useful extra trick.
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 surface apart. Even crank bearings benefit at starts, stops or when extreme shock loads upset the “hydrodynamic” film. (Are you listening, all you rally drivers and off road fanatics?)

Synthetic Hydrocarbons or POA’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 when the heat is on, 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.

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 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.

Must Have MORE Power!

Motorcars are bought for all sorts of reasons, but enthusiasts like lots of power. To get more power, a lot of fuel must be burnt, and more than half of it, sadly, gets thrown away as waste heat. For every litre of fuel burnt, 60% of the energy goes as waste heat into the exhaust and cooling system. A turbocharger can extract a few percent as useful energy and convert it into pressure on the intake side, but only 40-45% is left, and only 25% actually shows up as BHP at the flywheel. 6% goes in pumping air into the engine, 6% as oil drag losses and 2-3% as engine friction. The oil deals with 97% of the friction; so reducing the remaining few percent is not easy. If you doubt that even ordinary oil has a massive effect, take a clean, dry 200 bhp engine, connect it to a dyno and start it up. It will only make 1 bhp for a few seconds. Now that’s real friction for you!

Oddly enough, people get starry-eyed about reducing friction, especially those half-wits who peddle silly “magic additives”, which have not the smallest effect on friction but rapidly corrode bearings and wallet contents. In fact, even a virtually impossible 50% reduction in the remaining engine friction would be no big deal, perhaps one or two bhp or a couple of extra miles per gallon.

Even More Power!

He place to look for extra power is in that 6% lost as oil drag. In a well-designed modern motor, the oil doesn’t have to cover up for wide clearances, poor oil pump capacity or flexy crankshafts, so it can be quite thin. How thin? Well take a look at these dyno results.

A while ago now, we ran three Silkolene performance oils in a Honda Blackbird motorcycle. this fearsome device is fitted with a light, compact, naturally aspirated 1100cc engine which turns out 120+ bhp at the back wheel. The normal fill for this one-year-old engine was 15w-50, so the first reading was taken using a fresh sump-fill of this grade. (The dyno was set up for EEC horsepower, i.e. Pessimistic)

15w-50
Max Power 127.9 bhp @ 9750 rpm
Torque 75.8 ft-lbs @ 7300 rpm

After a flush-out and fill up with 5w-40 the readings were;

5w-40
Max Power 131.6 bhp @ 9750 rpm
Torque 77.7 ft-lbs @ 7400 rpm

Then we tried an experimental grade, 0w-20 yes, 0w-20! This wasn’t as risky as you may think, because this grade had already done a season’s racing with the Kawasaki World Superbike Team, giving them some useful extra power with no reliability problems. (But it must be said, they were only interested in 200 frantic miles before the engines went back to Japan)

0w-20
Max Power 134.4 bhp @ 9750 rpm
Torque 78.9 ft-lbs @ 7400 rpm

In other words, 3.7 bhp / 2.9% increase from 15w-50 to 5w-40, a 2.8 bhp / 2.1% increase from 5w-40 to 0w-20 or a 6.5 bhp / 5% overall. Not bad, just for changing the oil! More to the point, a keen bike owner would have paid at least £1000 to see less improvement than this using the conventional approach of exhaust/intake mods, ignition re-mapping etc.

Am I recommending that you use 0w-20 in your cars? Well, perhaps not! The PRO S 5w-40, which is a “proper” PAO/Ester shear-stable synthetic, will look after a powerful engine better than a heavier viscosity “cave at the back” conventional oil, and provide a useful extra few BHP.

The End

However, as with all good things in life, we don’t live in a world of perfect motor cars and therefore we have to look at the lubrication trade-off between longevity, reliability, power and cost, relative to the vehicle in which the oil is being used (a scruffy old XR2i with 192,000 miles on the clock is a very different proposition to your track day car). You could however look at a "true" synthetic 5w-40 or 10w-50 for competition and track-day use, but only the most committed competitor would want, or need, the 0w-20 for the extra 5% power.
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Received a confirmation on first fill of the Carrera GT. It is indeed a GT1 0W-20. This seems strange because the specs do not reach the approval. My contact explained they do have a first fill approval but do not have the after-market approval. The extra costs of this approval are weighing to much against the amount of Carrera GT's out there. Apparently this GT1 0W-20 has the right break-in capabilities. After this first fill, consumer will use the A3-based oils anyway.
Easy,

Referring to this article last paragraph.

So is it Dyno Oil ?
First Fill
Then A3


Using synthetic-oil in engine break-ins
By Road & Track, Technical Correspondence Column, July 2000 issue


Many readers have questioned us on engine break-in procedures when using synthetic oil. Conventional wisdom has it that a new or freshly rebuilt engine should be broken in using mineral oil, then, once enough mileage has accumulated to ensure rings and cylinder walls have lapped themselves into harmony, synthetic oil can be used.

Readers have correctly pointed out that several major brands come from the factory with synthetic oil, among these being Corvette, Mercedes-Benz and Viper. How can these engines break-in if run on synthetic oil from day one, they ask?

To find out, we spoke with Mobil and Redline Oil companies for their take on the synthetic break-in question. Mobil's response was that engines break-in just fine on synthetics, and that any wear point in the engine significant enough to be an interference, and thus susceptible to rapid wear, would be a wear point no matter what lubricant is used.

Redline, on the other hand, has found it best to recommend a mineral oil break-in. Occasionally an engine will glaze its cylinder walls when initially run on Redline, they say, so by using a mineral oil for 2000 miles, verifying there is no oil consumption and then switching to the synthetic, glazing is eliminated.

Cylinder-wall glazing is not a deposit left on the cylinder wall, but rather a displacement of cylinder-wall metal. This happens when the high spots of the cylinder wall crosshatch are not cut or worn off by the piston rings, but rather rolled over into the valleys or grooves of the crosshatch. This leaves a surface that oil adheres to poorly, against which the rings cannot seal well. Compression is lost and oil consumed, and the only cure is to tear down the engine to physically restore the cylinder-wall finish by honing.

Why is glazing not a problem for the major manufacturer? Because they have complete, accurate control over their cylinder-wall finish and ring type. Redline deals with a huge variety of engines and manufacturers, both OEM and from the aftermarket. Cylinder-wall finish and ring type thus vary greatly, and glazing can therefore occur, albeit rarely.

While we were at it, we queried about synthetic oil-change intervals. Mobil says to use the maximum change interval specified by the engine manufacturer, regardless of oil type. Redline said that once past an OEM warranty, anywhere from 10,000 to 18,000 miles, or one year, whichever comes first, is appropriate depending on conditions (dust, short trips). They also recommend changing just the oil filter at 6000 to 7000 miles as a precaution against overloading the filter. Redline further noted a caution when using synthetics with leaded fuels, as synthetics do not hold lead in suspension as well as mineral oil. Aviation is one area where leaded fuel is still widespread, and avgas is often used by off-road and racing enthusiasts, so a relatively short oil change interval may thus be indicated.


--------------------------------------------------------------------------------
Synthetic Break-in
By Tom Wilson
Road & Track, Technical Correspondence Column, November 2001 issue


Exxon/Mobil's official policy is that their synthetic oil may be used at any mileage, including factory fill, unless otherwise stated by the vehicle manufacturer. Mobil pointed out, as you did, that all Corvettes, Vipers, Porsches and Aston Martins are factory filled with Mobil 1 synthetic. We can only conclude that improvements in cylinder-wall finish and ring design or materials makes this possible.

It is also likely that vehicle manufacturers not using synthetics as the factory fill are also not optimizing their cylinder and ring packages for the slippery sythetics, in which case approximately 1000 miles on mineral oil should prove ample break-in time. In fact, in modern engines a very high percentage of ring break-in takes place very quickly, probably in the first 10 to 20 minutes of engine running. Certainly, some final lapping of the rings and cylinders takes place over several hundred miles after initial break-in.

Just to add some confusion, Porsche dynos all of its engines before installing them in the chassis. We were unable to determine what oil is used for the dyno session, but would presume it's Mobil 1
Im not aware of the reason they're using it and I'm not justifying it either. I'm only telling what I hear from the industry. As an OEM data provider we have contacts with approx. 30 different companies (times 19 for each seperate country in Europe) so I hear some things...

It's quiet possible they use Mobil in the States. There is a good change that the US philosophy differs from the European, simply caused by different lubricant markets, base-oils and blenders. Maybe they choose the 0W-30. but as long as nobody comes up with the OEM specs, we stay in the dark.
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