Why Turbo Engines Need Different Oil From NA Cars

As emissions restrictions tighten and more automakers struggle to meet increasing CAFE standards, small-displacement turbocharged engines are becoming more and more common. A small, efficient, forced-induction four-cylinder engine goes further on a tank of gas (in theory, at any rate) and provides plenty of power for day-to-day driving. It's also smaller, lighter, and generally more efficient overall than a big old V6 or V8.

There are very few downsides to smaller, turbocharged engines unless you're a "no replacement for displacement" partisan. That's not to say turbocharging is perfect and without issue, though. Turbocharged engines are more complex than, say, a pushrod V8, and even the best built turbo can still fail disastrously if not cared for properly.

The best thing you can do for your turbocharged engine, aside from sticking to your maintenance schedule, is to use specially formulated turbo oil. Why, though? Do you really need a special, probably more expensive oil just because you have a turbo? Well, let's talk about it.

Yes, you need special oil formulated for turbos for your turbocharged engine. The reason is pretty simple and easy to understand — heat. Turbos are driven by your vehicle's exhaust gases. They're also both lubricated and cooled by your engine's oil. While running, a turbo can spin at speeds up to 300,000 RPM — upwards of 50 times the speed of an average engine at highway speeds — and are exposed to exhaust gases that can exceed 1,000 degrees Fahrenheit. The oil cooling a turbo can be heated up more than 400 degrees, which is more than twice as hot as a non-turbo engine. This extreme heat can lead to two deleterious conditions — turbo coking and oil degradation.

Turbo coking is caused by oil cooking and sticking to the metal parts inside of a turbocharger. This causes a sticky, sooty residue that can gum up a turbo's insides and cause it to wear out prematurely or fail spectacularly. This is especially common when using conventional oil as it's more prone to coking than synthetics. As for oil degradation, that's simply caused by overheating the oil. Most engine oils can't stand up to the intense heat inside of a turbo, and they break down quickly as they're cycled from the engine to the turbo and back. Overheated oils can quickly lose viscosity, which can lead to, you guessed it, excessive engine wear or even a catastrophic failure.

The best thing to do for your turbocharged engine is use oil made specifically for said turbocharged engines. If you're not sure which oil to choose or what weight to use, your vehicle's owner's manual should have recommendations for you.