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

It's not the usual blah, blah, blah

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  • Jon

    “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.”

    More reliable my backside! I have had more than twice the trouble with computer controlled vehicles I ever had with my old carburetted cars. What people consistantly refuse to recognize is that the computer controlled vehicles require a phalanx of electrical sensors, many of which are more fragile (and therefore more prone to breaking or wearing out) then most mechanical parts. When there are twice as many things that can break, it’s twice as likely that something will. It’s simple logic. Also, with all the extra garbage under the hoods of today’s cars, repairs are much more difficult to make, if not impossible, with the simple toolbox full of hand tools that I used to use. Nowadays you have to take the car to the shop and pay to have it plugged in and analyzed before any work is even done, just to figure out what broke (usually one of the sensors that the computer requires). Before computers, you could usually diagnose the problem simply by what the car was or was not doing.

    Oh, and the screws on my carburettors never “wiggled out of position”. That is another problem that largely ended well before electronic fuel injection was used.

    You can take your new cars, I don’t want them. Oh and before the computers, you could tune your own car to get better performance or better fuel economy without leaving your own driveway, an usually with nothing more than a screwdriver and a couple other basic hand tools.

    As with many areas of life, computers add a little convenience to cars because there is less routine maintenance, but in te long run add a lot more headaches because we become reliant on them and then they break. Plain and simple.

    • Me

      I sold a new car since if was the biggest piece of crap I ever owned. I had sold an old 89 Dodge Daytona for a new Dodge. Nothing but problems. Can’t really work on it like my old cars. Me and my family ALWAYS worked on our cars and kept them for over 10 years. I seen this Dodge as a throw away car. I hate to say that’s totally bull about the screws loosening on a carb. I’m a older woman and I never had anything happen like that. I did 99 percent of all the work. People have NO idea how easy and tough the old cars were. Yes maybe the gas mileage might have been worse, But I have NO CONFIDENCE IN NEW CARS. I bought an older Mustang and that seems to be doing the job.

  • GT

    I’m no mathematician but if these devices saved you 1 mile per gallon and it costs $2 a gallon for gas then you would have to drive less than 500 miles in order to recoup your costs. Well worth getting a good ECM.

  • Me

    Anyone can write a review like this. Notice he said “Probably not”. You have search the forums, One for your car. Ask questions.

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