For road warriors who spend endless hours commuting or traveling, the usual AM, FM, or satellite radio offerings can grow tiresome. People want their own playlist.

To address the growing desire for audio binging, Pandora, Spotify, and Slacker have smartphone apps that wirelessly deliver customized music to your phone. In turn, the phone can then stream it to your car’s audio system via Bluetooth, USB, or AUX connection.

There’s one big problem: Streaming audio in your car—especially in high-quality sound formats—can eat up enormous amounts of data. If your cell phone plan has a cap on how much data you can download from the Internet before you get hit with excess charges, you might be in for a shocker when you get your bill.

How Can You Avoid This?

First of all, Pandora and Spotify default to a lower-fidelity setting when their apps detect you are streaming through cellular data. While that means you're using less data, you're also listening to something that sounds like a transistor radio inside a 32-gallon trash bin.

But both apps allow you to crank the streaming settings to a higher-quality sound, which means more data streaming to your phone.

In Pandora’s case, neither the base audio setting nor the upgraded setting will burn through a single gigabyte of data, unless you are listening for weeks at a stretch while driving. So it’s well within the parameters of most cell phone data plans. However, even at the upgraded 64Kbps, the quality of Pandora mobile streaming is fairly weak—well below that of a clear FM signal, and far thinner sounding than the top quality of an Apple iTunes song file.

Does this matter? To an audiophile, it does. The more bytes, the clearer the treble, the deeper the bass, the greater difference between loud notes and subtler ones.

Spotify, by contrast, offers far higher-quality streaming, up to 320Kbps—although it also has lower-res 96 and 160Kbps settings. But as we’ve proven in tests here at Consumer Reports, if you have even a decent sound system in your car, you truly can hear the difference between low- and high-quality streaming.

The downside: Spotify’s stereophonic sound spectacular burns through data, to the tune of 1.2 gigabytes an hour. So if it’s crucial to hear the second violin section in Mozart’s Jupiter symphony while driving to orchestra rehearsal, you could use up your monthly data plan during the molto allegro.

One workaround is to subscribe to Spotify Premium for $9.99 a month. It lets you create custom playlists and download them at home for later listening—when normally you would have to stream them from a cellular network.

That means anything downloaded over WiFi won’t count against your cell data plan. Spotify lets you download up to 3,333 tracks on as many as three devices, so that’s 9,999 tracks in total across, say, a tablet, PC, and phone.

Slacker offers a similar solution with its custom-playlist software. A spokeswoman for the app says the recommended way to use Slacker is to create your own custom playlist of music, choosing from millions of songs and custom podcasts as well as multiple genres, and create playlists that you download while on WiFi. That lets you use the app while in transit without impacting cell data. However, if a Slacker user decides to stream—which the company doesn’t recommend—sound quality goes as high as a data-sucking 320kbps.

If you are hooked on podcasts, there is a similar methodology.

For Android, we like Podcast & Radio Addict, as well as Downcast for Apple’s iPhone. Both allow downloading or immediate streaming. Even though file sizes for podcasts are usually modest (about 50MB for one 25-minute episode of Talking Cars With Consumer Reports), if you wanted to have an entire season of This American Life on your phone during a vacation, pre-loading means you won’t chew through your cell data.

A final, more expensive workaround: Many new cars hitting the market today have their own embedded WiFi hotspots. For some infotainment head units, you can stream music with the car’s onboard modem or Internet connection that is bundled with unlimited Internet service. That means when you connect your phone to the car’s infotainment system, you are effectively linked to the Internet via the car’s telematics system, rather than through the owner’s smartphone cellular network. However, once any free trial period ends, you must sign up for an additional data contract to continue this service.

How to Use Spotify and Still Save Your Data Plan

Want to listen to music on the road at high fidelity without torching your cell phone's data plan? Spotify has a hack that allows you to do just that.

Once you’ve downloaded the Spotify app, and paid for premium service, open the app. From the main menu tap on "Your Library." Once the Library page opens, tap on "Playlists." Then, tap on the "Edit" icon in the upper-right corner, and then the "+" sign in the upper-left corner to create a new playlist.

A "New Playlist" icon box will pop up. Type in a name. Tap the "Create" response, and you will see your new playlist listed on your Playlist page. Click on the newly created playlist icon.

The next page shows that nothing is in the playlist's folder, and it will suggest you browse to add content. The Browse button allows you to click through numerous genres to populate your playlist. If you don’t have time to poke around, swipe from left-to-right and click on the "Search" command to seek a specific artist or composer.

Once you find the music you were hunting for, tap "Follow" and the “Available Offline” slider will appear. Slide it over and the tracks will download over WiFi, playable without cellular data once the download is complete.

One final note: Before you set out on your journey, be certain your Spotify app is offline and not using celluar data. To do that, go to the app's home page, tap the icon of three bars in the upper left corner, which brings you to a main menu, then tap on the symbol that looks like a bicycle gear, located in the lower right corner. Then tap “Playback,” which brings up a page that shows an “Offline” slider. Tap the slider so that you’re certain Spotify isn’t using your cell data.

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