Does oil change affect performance?

This is a simple question that we rarely think to consider. Does an oil change affect my car's performance? If I don't change my oil often enough, will my performance go down? What if I change it more often? Am I even clear on what I mean when I say 'performance' in this context?

The value of proper oil changes

The first thing we need to be clear on is that changing oil at the proper time is the best thing you can do for the life of the engine. You can use fuel additives to keep the injectors clean. You can use the right octane rating of gasoline. You can do lots of things, big or small. But changing the oil within the recommended period (every 5,000 - 7,000 miles for most manufacturers) is the number one thing that will keep any car or truck running well for its entire vehicle life.

Not changing your oil often enough allows harmful dirt, particulates and acids to degrade key engine parts. It also increases the buildup of sludge and lessens the oil's ability to dissipate heat, increasing engine stress. So not changing your oil often enough is a bad idea. But what effects does it have on performance?

Performance? What's Performance?

When we say 'performance', we mean gas mileage primarily.  Running an engine on old, sludgy oil will cause a decrease in fuel economy. How much? The book's still out on that; we're not aware of any good automotive engineering studies that have quantified the effect.

But when oil thickens and becomes sludgy because it's past due to change, it loses some of its lubricity and makes the engine work harder. Old oil will break down due to exposure to heat, losing its ability to maintain the viscosity needed to do its job. Without the right viscosity, the oil loses the essential ability to get where it needs to go in the engine. The engine runs hotter and less efficiently, robbing the engine of both gas mileage AND horsepower.

How Sludge Affects Performance

Old oil past due for a change is a recipe for developing oil sludge. This thick sludge can block key pathways of oil flow, limiting the oil's ability to flow where key parts need it to be. These parts don't get the lubrication they need. The sludge also insulates hot parts of the engine, which is a bad thing. Part of the function of oil is to draw heat after from engine parts. If they're covered in sludge, they stay hotter longer and their life is reduced.

So the basic answer to the question does oil change affect performance is pretty easy. Old oil will reduce engine performance, lower its horsepower, reduce its mileage and eventually shorten its life. Be sure to get your oil change in accordance with the recommendations of your vehicle owner's manual.

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