Should You Hack Your Car for Better Mileage?

A device called a power programmer promises to let you hack into your car’s computer to improve your gas mileage. But is the cost worth the benefit?


In the olden days (before the 1980s), things like the mixture of fuel and air pumped into your car’s engine were regulated by mechanical parts, normally a carburetor. Now, nearly every car on the road accomplishes this task with – what else – a computer.

As with many areas of life, computers add efficiency to cars. They’re more precise, which often makes them more economical, as well as a better choice for optimizing smaller engines to deliver more horsepower. In addition, since a computer will never wiggle out of position like screws in a carburetor might, they’re also more reliable.

It should come as no surprise that the computer in your car – often called an engine control unit (ECU), a power-train control module (PCM), or an engine control module (ECM) – isn’t always tuned for your individual preference. Auto manufacturers look for a balance between power and fuel economy when releasing a car to the public. Some people want a sporty car while others want an economical one.

Which leads to a question: Is it possible to get a computer chip or reprogram your car’s existing computer to deliver better mileage? We did a little research to find out…

There’s a class of products that allows you to take control of your car’s computer and reprogram it to better fit your individual needs. They’re called “performance chips” and are commonly found in the kinds of cars you’d see in The Fast and The Furious. Auto tuners and street racers use them to get more horsepower out of their engines, often by increasing the amount of fuel their engines burn. But the reverse is also theoretically possible: You can turn down the fuel consumption of your engine by installing a performance chip. With the right one, you can sometimes even program your car’s computer to use a less-expensive, lower-octane fuel.

There are three kinds of performance chips – control modules, power programmers, and engine management systems – but we’re only going to focus on the first two.

A control module sits between your car’s computer and the various sensors monitoring your engine, feeding slightly altered information back to the computer in such a way as to trick it into doing what you want. Power programmers, on the other hand, completely reprogram your car’s computer. Because of the way each works, control modules must be permanently installed in your car, while power programmers only need to be attached for a brief period of time to reprogram your computer.

Installing a control module or power programmer in your car shouldn’t void its manufacturer warranty. Federal law requires manufacturers to first prove the non-factory parts you installed contributed to any warranty-related damage before they’re allowed to renege on the warranty.

To find a control module or power programmer for your car, head to an auto parts website like AutoAnything and do a search for your car’s year, make, and model. Carefully review the options available to you, and read as much material as you can get your hands on before deciding how you’ll proceed. Check out reviews online, and make sure you’re comfortable with the entire process, from purchase to installation, before clicking “Buy.” You also want to make sure it’s returnable if it doesn’t produce the intended results.

If you’re not used to working on cars, you might want to find a friend who is or find a mechanic who’s willing to help. These devices are marketed as simple to use – you only need to plug them in and press a few buttons – but a modification to your car’s engine is something you want to be sure you’re doing right.

But here’s the problem: The general consensus is that, with the proper control module or power programmer for you car, you might see gains in mileage, but possibly only 1-4 miles per gallon.

Is it worth it?

Unfortunately, probably not. These devices cost anywhere between $250 and $500. Do the math and that means if you’re only gaining one mile per gallon, you’d have to drive more than 37,500 miles to save $250. And if you had a $500 performance chip, you’d have to drive 75,000 miles before recouping the cost. Granted, you could get a bigger mileage improvement, but the cost/benefit would still make this purchase tough to justify.

Better idea? Look at more typical ways to save gas – many of which are free – in stories like our 28 Ways to Save on Gas.

Stacy Johnson

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