OBD2 'fuel saver' boxes can actually increase costs by damaging your car - do this instead

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ZDNET's key takeaways

These dongles aren't tuning tools that will save you money.

They can damage your vehicle and cost you money.

You can take safer precautions to keep your car in good status.

Drivers will no doubt be aware that fuel prices are through the roof. This means scammers are out there trying to make money from people already feeling the pinch.

One thing that I've noticed making the rounds recently is "fuel saving" "economy chip tuning box" OBD2 dongles. I've had quite a few readers ask me to think about them. So let's take a look inside one of the most common ones I've seen, and see why, at best, it's a box with blinky lights, and at worse, it's something that can damage your car.

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This is one of many fake fuel savers out there. The good news is that they're all easy to spot -- they all look pretty much the same, the wording includes techie stuff like "OBD2" and "tuning box," and they push simplicity of use ("plug and drive" is a common phrase), and make totally over-the-top promises when it comes to fuel saving.

Note: OBD2 is a car term, and is stands for On-Board Diagnostics II and it's a built-in, system that monitors engine health, emissions, and even shows access to live data. There are legitimate tools (both cheap and expensive) that can be used to interface with the OBD2 port, and allow you to learn a lot about what's going on with your vehicle.

The lie that you're told on the box and the sales literature is that you plug the dongle into your vehicle's OBD2 port, fiddle with the reset button on the dongle, start the car, watch the cool blinky lights, and the dongle will remap your car's computer as you drive, saving you money and lowering your emissions.

Sounds too good to be true, right? Well, you know what they say!

As for price, I've seen these vary from a couple of dollars to over $30 for two.

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Here's what you get.

The dongle and the literature look good and make some big promises. I even get a 2-year warranty! Wow!

The problem is, there's nothing inside beyond the circuitry needed to make some LEDs blink. Yup, really. That's all it is. I took one apart, and there I found a timer chip, a few LEDs, a few resistors, and a button.

Only three of the prongs are connected to anything!

It'll blink if you connect it to your car (I'm not going to do that, and I'll explain why in a bit), but I can make it do the same blinking by connecting it to a 12V power supply.

It's a modern smoke-and-mirrors trick. So why don't I like these?

Well, beyond the fact that people are paying good money for a box that flashes, these can cause problems. I've seen badly assembled examples where bits of solder and wires rattle around inside, which could cause short circuits and even fires (and let me tell you now, a car fire is really bad news).

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The other problem I've seen with these sorts of dongles is that the pins can come out and get stuck in the car's OBD2 port, potentially damaging it.

Damage your car's OBD2 port, and you're looking at a seriously expensive repair.

Want to save money every time you drive? Forget the scam dongles and do the following:

Make sure your tires are properly inflated: Tires that are 10 psi below the recommended pressure (and this is incredibly common) can reduce fuel economy by as much as 3% (not to mention wearing out your tires faster than normal). A tire pressure gauge and small inflation pump will pay for itself.

Drive nice and smooth: Hard acceleration and braking might be fun, but it costs money.

Reduce weight and air resistance: Remove all unnecessary junk from the trunk, and put that roof rack, bike carrier, or car roof tent away when it's not in use. I took the roof rack and light bar off my truck last year, and there was a noticeable improvement in fuel economy.

Keep up with maintenance: It makes a real difference in both fuel efficiency and your vehicle's longevity.

Do this, and don't plug sketchy things into your car.