Why Does Oil Burn Off?

Here are the main reasons why engine oil burns off in an engine:

1. An oil was put in whose parameters don't suit this engine. To find out how to figure out which oil suits your engine, read the articles on carmakers' approvals, and also on how to correctly choose oil for an engine. Short and to the point — oil that's too low in viscosity will simply stay in the cylinders and burn off, while oil that's too high in viscosity will build up too thick a film on the internal walls. Either way, this leads to increased oil consumption.

The cure is dead simple — put the right oil in the engine. You'll be surprised how much this can affect engine-oil consumption. Among all the options approved by the carmaker for this engine, you should pick the oil with a higher viscosity than what's currently in there. Switching from a synthetic oil to a semi-synthetic very often solves the oil-consumption problem, truly. And there's no harm to the engine at all, provided the semi-synthetic with these parameters doesn't conflict with the carmaker's recommendations.

2. Worn valve seals (oil-control caps). In many engines these seals can be replaced without even removing the cylinder head, and the price of this strategically important part will surprise you with how small it is. And oil consumption can drop several times over. The problem can only be diagnosed indirectly, by compression readings, but you'll only know for sure after the replacement. The cause of worn valve seals is temperature swings, or an unsuitable engine oil that's incompatible with the rubber they're made from.3. Worn piston (oil-control) rings. There's nothing to be done here — ideally the rings need to be replaced, and in most cases that turns into a full engine overhaul. Though you can also try the so-called “ring decoking” (often helps cars after a long period of standing idle). The simplest way to “decoke” is to get out on the highway and drive ten or twenty kilometres at noticeably higher revs, closer to the red zone on the tachometer. There's also special chemistry sold for this, added into the spark-plug holes before “decoking,” but honestly — how safe that chemistry is for the engine down the road is a big question mark for the author of this article.

4. Damage or wear to the internal surfaces of the cylinders (scoring), as well as to other internal engine parts. Problems like these simply can't be fixed and are usually accompanied by unusual noises while the engine is running. The cause of these faults is dust and dirt getting into the engine, late oil and filter changes, poor-quality oil, the use of third-party additives, and much more. It should be said that simply an engine's age or mileage alone can't cause a sudden jump in oil consumption — in that case consumption rises gradually and very slowly.

The remedy in this case — try switching to a higher-viscosity oil anyway (among the options allowed by the engine manufacturer's approvals), replace the valve seals, and see what the oil consumption looks like afterwards. If it comes out to a few litres between changes, it's cheaper to simply top up the oil while setting money aside for a new engine or car. An overhaul in this case is a lottery with very slim odds of success.

5. High crankcase gas pressure, or a failed turbo (compressor). In cases like these, oil gets into the cylinders directly through the fuel injection via the crankcase ventilation system. High crankcase gas pressure is typical of worn engines and results from the causes described above, while a turbo can be repaired or replaced. What's more, a faulty turbo (compressor) is fairly easy to diagnose.