It is likely to take a few thousand miles, though some engines may reach maximum fuel economy before then while others may require more time and use. An engine is fully broken in once all the mechanical parts are properly “seated” and there is no longer any new-car tightness or friction in the vehicle’s operation.
Most vehicle owner’s manuals contain a few words of wisdom about the break-in period. Typically, that entails taking it easy for the first 1,000 miles, such as avoiding full-throttle acceleration or cruising at the same speed for extended periods so the engine operates under a greater range.
However, you will not see a statement about when you should expect to get maximum fuel economy — only tips on how to improve your mileage. That’s because of the classic don’t-blame-us warning: Your mileage will vary due to different traffic, weather and road conditions, and your driving style.
So when should you expect your best mileage from a new vehicle? After at least a few months of local and highway driving, when your tires are fully inflated, the weather is warm, the wind is calm, your car has no mechanical or electronic issues and you are operating at your best. That means you’re driving with a light throttle foot, being patient in traffic, using the brakes as little as possible and acting as if gas were real expensive.
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