Burning oil: how to spot it in the exhaust

Burning engine oil is fairly easy to diagnose on its own. Burning inside the engine, oil produces bluish-grey smoke in the exhaust, which can't happen when quality petrol burns (black smoke, as a rule, points to a fuel injection fault). On top of that, if an engine burns more oil than it should over an extended period, a black oily ring forms at the edges of the exhaust pipe.

It's a lot harder to work out why the oil is burning. Without opening up the engine, nobody can tell you the exact cause of increased oil consumption. But there are a number of relatively cheap and simple ways to fight oil burn that you can try before opening up the engine.

For starters, it's worth noting that oil burns off in every engine! It simply cannot avoid burning off at least somewhat, since it's constantly forming an oil film on the inner surfaces of the working cylinders, where the fuel ignites. What matters far more is exactly how much oil is burning off in your engine, and what the normal rate of burn is for it.

The next important point is that the amount of oil burned off depends directly on how the engine is run. Generally, the higher the rpm an engine runs at, the more oil it burns, and this has nothing to do with the actual condition of the engine itself. The laws of physics are at play here — the higher the rpm, the higher the temperature of the engine and the oil, and so the thinner the oil, which means more of it stays in the working cylinders.

All of the above means that before passing judgement on your engine, you need to take into account both how the engine is run and its design features (every engine consumes oil differently — in V-shaped engines, for instance, a lot more oil is usually burned off than in inline ones). As for these design features, try reaching out to your car brand's official representative, or search online for your specific engine — there's plenty of that kind of information out there.