Does hitting the redline help or hurt your car?

There’s an old tale that Ferrari mechanics would often run their clients’ cars up to redline for extended periods after servicing to break loose the carbon deposits within the engine—a process that became known as the “Italian tuneup.” But just how effective is this technique at removing carbon buildup? Engineering Explained’s Jason Fenske explores three key areas to determine if there would be any benefit to periodically redlining your engine.

The first consideration is the temperature at which carbon deposits form. Fenske cites research indicating that these deposits generally latch on between 195–290°C (about 380–550°F for imperial users), with highest levels occurring at 200°C (392°F). These temps are pretty hot, but certainly within the normal operating range for components in a modern-gasoline-powered engine.

But how much heat is needed before those deposits begin to deteriorate? As it turns out, internal temperatures need to reach a toasty 325°C (617°F) before decarboxylation occurs, effectively breaking down existing carbon buildup and preventing new deposits from forming.

As for whether an engine can reach those lofty temps, the answer is complicated. While pistons and exhaust valves can easily meet or exceed those numbers, intake valves generally run on the cooler side of the spectrum. Cars equipped with an upstream fuel source, such as port fuel injection, might have trouble getting hot enough to start the breakdown process. Newer direct fuel injected engines actually saw increased carbon deposits with higher engine loads.

So while we can conclude that pistons and exhaust valves might benefit from a few hard runs to redline under load, it’s not 100-percent clear if intake valves would see the same perks from doing so. Research aside, however, we do know that zinging your car to redline will result in big smiles and increased happiness.

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    This was also Bill Cosby’s excuse for speeding — he was “Getting the gunk out”; to which the PoliceOfficer replied, “Maybe we’ll get the gunk out of you!”

    Apologies to everyone, concerning Rodney King.

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