F1's major engine controversy explained

Pre-season testing and the early races of each Formula 1 season always spark some controversy based on creative interpretations of the 105 pages of technical regulations that govern the design of the cars. It's the first time that rival technical directors get a look at the opposition, and inevitably this leads to discussion of the semantics that may be used to form the understanding of those regulations.

I've mentioned oil burning briefly before, but since interest in this abstruse subject - which many thought had been put to rest - has been sparked afresh, it's worth revisiting and examining in more detail.

Perhaps the first thing to point out is that the use of lubricating oil to enhance power through improved combustion is not new. In the last era of turbocharged engines some pretty exotic but highly lethal fuels were used. These were pioneered by BMW, which had supposedly found the formula through reading papers regarding fuel development for the highly boosted engines used by the Luftwaffe fighters in World War II.

These fuels bore little or no resemblance to petrol, and indeed the rules didn't require that they should. Instead they were a mixture of hydrocarbons; the majority was blended from benzine, xylene and toluene. The primary component was the toluene at close on 85% of the fuel mass, which had an octane rating of 121, significantly higher than the 100 octane standard aviation fuel.

Unfortunately, toluene is highly carcinogenic. Having contemplated the implications, after a short while the FIA defined a fuel for the engines that was much closer to road fuels. This left the engine developers with a problem as they could not run the boost anywhere near as high as they would like, since the new fuel didn't have the anti-knock properties of the recently banned fuel.

Some of the more resourceful realised that while the fuel may be limited, the oil wasn't, and on any engine it's normal for a small quantity of oil to enter the combustion chamber, either through bypassing the piston rings or through leakage of the valve guides.

1% more 'fuel' would achieve 1% more power

In addition, it wasn't too difficult to contrive a system on a turbocharged engine where the oil used to lubricate the turbo bearing could be encouraged to leak into the compressor and hence find a direct path to the combustion chamber. It wasn't long before the lubricating oils were being doped with anti-knock compounds to allow modest increases in boost. This wasn't illegal; it was just an example of the rulemaker being one step behind the rule exploiter.

If we now fast forward to 2014 we had the potential to revisit this contrivance but for slightly different reasons.

That year, the current hybrid power unit was introduced. Just as significant as its novel architecture was the fact that this was the first F1 engine to be governed by a fuel-flow limit. Until then, all normally aspirated racing engines had been designed on the principle that one needed to get as much air as possible into the engine and then inject the right amount of fuel to obtain best torque.

One kilogramme of gasoline contains around 43 megajoules of energy. The 2014 regulations decreed that the maximum fuel rate was 100kg/hr or around 28 grams a second. Irrespective of efficiency, this means that the maximum available chemical energy is now dictated by the fuel-flow limitation. Consequently if you could add 1% more 'fuel' with an equivalent chemical energy, then you would achieve 1% more power on the assumption that the thermal efficiency remained the same.

People soon realised that this additional 'fuel' might be added through combining additives to the lubricating oil and then contriving for that fuel to enter the combustion chamber in a controlled manner.

Over and above the possibility of simply increasing the calorific value, or chemical energy available, it was soon realised that the old anti-knock chemicals could be of even greater value and it's likely that this was the road once again travelled.

In addition, due to a ruling made some years ago it was a requirement that the engine breather was vented into the air box. An ideal route to inject the additive and one that could be controlled by a separate valve if necessary.

During 2017 it was accepted that the chemical definition of oil was free but that oil consumption must be limited to 1.2 litres per 100km or around 0.06 litres a lap, while new engines introduced from the Italian Grand Prix in September would have to adhere to a limit of 0.9 litres for every 100km. For '18 that original limit has been halved and the teams must supply the FIA with a continuous measurement of engine oil level. There's a ban on active valves into the engine air intake too.

Perhaps most importantly there's a new Article 20 that defines engine oil in such a way that to comply, oil must now be essentially a substance that we would all recognise as a lubricant.