Oil formulas unleash hidden powers

IT might look like the same old brown, slippery liquid motorcyclists have poured into their engines for decades, but there’s as much high-tech computer-aided design going into some modern oils as there is into the bikes themselves.

A visit to Castrol’s Technology Centre at Pangbourne, Berks – one of the most advanced of its kind in the world – reveals testing is an amazingly precise art and that there is a whole range of additives available to shape the qualities of oil. And chemists are constantly working on new ones to change the properties of the base oil.

For example, a common additive is called CPT (calcium petroleum sulphate) which cleans pistons. On two-strokes it is particularly effective at cleaning the ring grooves.

So if there are signs of gummed-up ring grooves in an engine after it has been tested, the engineers tell the chemists, who reformulate the oil to deal with the problem.

Castrol’s latest " designer " oils are tailored so specifically that the firm even recommends different oils for the same engine depending on how it is going to be used.

For example, if your Kawasaki ZX-9R is your everyday, get-to-work transport, Castrol will suggest a different oil than for the riders who use theirs for regular track day thrashes.

A fully synthetic oil, such as a 5W-40, costs around £30 for five litres. It will give you a power gain of around two per cent compared to a cheaper semi-synthetic 10W-40 favoured by the commuter. That’s a gain of more than 3bhp on a ZX-12R or Hayabusa and close to that for most modern superbikes. Many aftermarket cans struggle to match that.

The W number in the oil’s labelling refers to its viscosity when cold. The 40 refers to the viscosity at 100° Centigrade. The lower the W number the thinner the oil is and the less it resists the spinning of the engine. Thicker 10W-40 lubricant gives your engine its best chance of a long life, though.

Brian Utton, who develops new oils for motorcycles at Castrol, says you can get them with a viscosity as low as 5W-30, but many manufacturers don’t recommend it.

You can check which suits you on the oil selector on Castrol’s web site: castrolbikeworld.net

To discover the effectiveness of the oil engineer’s manipulations, it’s crucial they have a set of reliable test procedures which repeatedly simulate real world conditions. When a new oil is tried out, the engineers have to be certain that any changes they find are only due to the oil itself. The basic testing device is, of course, an engine.

The huge range of engines in Pangbourne’s labs (from small racing motorcycle two-strokes to giant marine diesels) come fresh off the production line. But the first thing Castrol’s engineers do is strip them right down. This is because there are always small variations between individual power units due to the tolerances which have to be allowed for in mass production.

A tiny variation in the fit of a piston ring in its groove, for example, can affect how much pressure from the combustion chamber escapes past it, and how much carbon forms on the side of the piston skirt – something engineers will be keen to measure.

So each new engine is pulled apart and " standardised " , a procedure similar to the blueprinting process conducted by tuners the world over.

All the significant tolerances are accurately measured and readjusted to the values originally intended by the designer. This is usually done by picking out components from a wide selection of apparently identical production items, but which in fact are each very slightly different. Conrods might have slightly different lengths, pistons will have small differences in width and shape, and even some head gaskets will be thicker than others.

Many manufacturers co-operate closely with Castrol in this process, as the engine designers need to know what is happening inside their engines as much as the oil engineers.

Once an engine has been rebuilt to standardised tolerances, it can be fitted to a dyno and run, using the new oil.

The test might simply involve an engine being held at a constant rpm and load, but much more likely the whole operation will be computer controlled to simulate the worst, most mechanically unsympathetic rider or driver you’ve ever met. A typical sequence might include starting the engine from cold then spinning it straight to the rev limiter in a silicon chip traffic light grand prix, bimbling around town for an hour in hot conditions, then blasting down a (Gatso-free) motorway flat-out before stopping and deciding to top-up the searingly hot radiator with ice-cold water. And this sadistic treatment might be inflicted using only a third of the volume of oil the engine designers intended.

Another programme used by Castrol is an exact simulation of a top racer thrashing a Honda CBR600F around Brands Hatch.

The dynos and computers are capable of compressing a year’s hard life into a few days of engine hell in the lab. Then the tortured motor is pulled apart to see what has gone on inside.

The measurements required are so accurate that the individual components of the engine have to be left in a controlled environment for 24 hours before they can be measured. Even the tiny expansions in metal which occur on a hot day are enough to upset the accuracy. The engineers look at how much and where carbon has built up, how components have worn and even how the surface hardness has been affected (which is important to the life of camshaft lobes, for example).

The power output of the engine while it was on the dyno will also have been recorded – with the CBR600’s virtual Brands Hatch laps the engineers know exactly how much power the motor was producing throughout the virtual race.

It’s here that the ability of thinner oils to reduce internal friction – and so increase power – become clear.

On two-strokes, sticking power valves can be a problem as carbon builds within the exhaust port, something Castrol measures by recording exactly how much electric current is needed to keep turning the power valve while the engine is being run.

As a result of these tests they have even devised an oil which not only stops carbon build-up, it even cleans off some of the carbon already in place, unsticking a previously problematic power valve.

It’s only after all the tests have taken place and the engineers know exactly what is going on inside an engine that they can go to the chemists to ask for changes to the oil’s formula.

But, sadly, what Castrol’s engineers won’t do is blueprint your engine for you…