Why Burn Engine Oil?
A bit of a stir occurred in F1 this 2017 season with regards to teams using engine oil in ways other than prescribed. Several teams are under suspicion of using oil to supplement their fuel and gain more power as a result, and whether this was clever innovation or just being sneaky is still being debated.
To put some context behind this, fuel in F1 is heavily regulated. You are strictly limited to 105kgs, and additives are restricted to tiny amounts - leaving the fuel used in F1 engines very similar to that of ordinary road cars.
However, oil was not as tightly controlled – both in the amount you could use and what you could add to it. There are still limits of course, but with a much wider degree of variance as to how much oil an engine gets through during the race, it gave teams more freedom to use it elsewhere.
What was particularly important was the lack of additive restrictions to oil. Chemicals and polymers that teams would very much like to add to their fuel but couldn’t, were instead added to their oil and intentionally bled into the combustion chamber in order to gain the benefits.
In a standard car, oil burning in the engine is a symptom of a problem. Either the piston rings have degraded and are allowing oil around the piston and into the combustion chamber, or the valve seals have perished and oil is leaking directly onto the piston head.
The engine will continue to run as long as it is kept topped up with oil, but as oil is not as combustible as fuel it is not ideally wanted in the chamber - and should be doing its job of lubricating the engine instead.
Fixing it is necessary if you want to pass your next MOT, and the environment will thank for preventing the blue puffs of smoke from your exhaust. It’ll also keep your wallet a bit happier at not having to keep buying replacement oil.
This would be the same in an F1 engine, if it wasn’t for those aforementioned additives. These additives can provide a host of benefits, namely boosting combustion and delaying ignition within the chamber.
This has the effect of timing the ignition so that all of the fuel/air mixture detonates at the same time and when it does detonate it does so more powerfully - providing a significant power boost that effectively raises the octane level of the fuel mixture.
There’s a number of ways of getting this oil mix into the combustion chamber, but due to the secretive nature of the technology involved not all of them are known.
One method understood is the addition of second set of injectors at the bottom of the cylinders - below the pistons and just above the crank shaft – which sprays a mist of oil onto the underside of the pistons.
When timed correctly on the down stroke, the increasing pressure in the crankcase will force the oil vapour through the oil ring grooves. Usually these grooves are positioned under the oil ring so they can fulfil their job of collecting the excess oil gathered by the oil ring and channel it back down into the crankcase. However if you modify the number and shape of these channels, and reposition them higher up in the ring seat, you can turn the oil ring into a valve of sorts and control the flow rate of oil allowing it to enter the chamber.
All of this works together to achieve a noticeable increase in performance by circumventing fuel limits and additive restrictions - hence the debate on whether it was within the rules or not.
For you average car this isn’t necessary at all. You don’t have a fuel limit or a restriction on what additives can be added to your tank and so circumventing these isn’t needed, and neither is burning oil. If your engine starts smoking excessively from oil making its way into the combustion chamber and being it burnt, it's still very likely you have a problem that needs fixing.