Published October 1, 2011. From Cook's Country.

The best traveling companion should open and close easily, seal tightly, and keep the contents hot. With hundreds of mugs out there, far too many miss the mark.

products tested (listed alphabetically)

‧Bodum Double Wall Travel Press with Bonus Lid

‧OXO LiquiSeal Travel Mug

‧Thermos Element 5 Travel Mug

‧Thermos Sipp 16-Ounce Vacuum Insulated Tumbler

‧Timolino Icon 16-Ounce Signature Vacuum Travel Mug

‧Trudeau Board Room 16-Ounce Travel Mug

‧Zojirushi 17-Ounce Clear Stainless Mug

Enjoying your own coffee or tea on the way to work beats spending $4 for a latte in a paper cup, but not if the vessel it's in offers no better heat retention and proves harder to sip from. After surveying the vast travel mug market, we narrowed our choices to seven, ruling out plastic and ceramic for lousy insulation, mega-mugs that hold 24 or more ounces (for the rare monster commute), and anything that requires complete lid removal (you're in transit, after all). Prices ranged from $15 to $39.

A travel mug is supposed to keep your coffee hot. Although experts disagree about the perfect drinking temperature, we find that coffee below 140 degrees is lukewarm, not hot. We filled the mugs with freshly brewed coffee at exactly 155 degrees. Then we threaded thermometer probes into the mugs so we could read their contents' temperatures over four hours without opening them. We knew from previous tests that ceramic travel mugs don't retain heat for longer than 30 minutes, plastic for about an hour. With only double-wall stainless steel mugs in this lineup, we were surprised that one lost heat just as quickly as any plastic mug.

Most of our mugs kept coffee above 140 degrees for just over an hour. A few mugs retained heat remarkably well: After three hours, one mug had "cooled'' to only 152 degrees. Another mug stayed between 145 and 150 degrees for more than two hours. We let colleagues test-drive these two mugs for a few weeks; users reported that with one model they had to wait a long time before the contents were cool enough to drink. The other model maintained an optimal temperature the longest, staying above 140 degrees for two hours.

We demand that our travel mug be rugged, with a snug-fitting lid that won't leak or drip, so we turned full mugs over and shook them. The good news is that all were leak-proof, but only when they were filled properly (overfilling disrupted the seal). One mug had no fill line; on the first try we overfilled it, and it leaked.

Mugs with complicated gaskets in their lids presented another problem: The gaskets trapped liquid, so when we closed the lids and began sipping, coffee dribbled out. Mugs that were hard to close all the way had us rechecking them before we put them in our bag, fearing a leaky mess.

When we filled the mugs with coffee for a car ride, we cottoned quickly to those we could open single-handedly, since that let us keep both eyes on the road. Mugs with handles didn't fit in all car cup holders, and using them distracted us from driving. One sleek, slightly curved tumbler uses a sturdy snap-open lid that proved simple to operate. Plus, the lid didn't partially obstruct our view!*the chief flaw of another mug (though that's not a concern for commuters who don't drive).

When you're drinking a hot beverage from a lidded mug, you need the flow of liquid to be predictable and manageable!*neither a torrent nor a trickle. The single half-inch opening on our favorite mug was neither stingy nor overly generous. Mugs with 360-degree openings let coffee rush out from too many exits.

We'd love to blast our mug clean in the dishwasher, but we'll take anything we can attack with hot, soapy water and a sponge. Narrow openings had us struggling to squeeze in a sponge. Mugs with wide bodies and uncomplicated lids that didn't trap odors, such as our winning model, made cleanup a breeze. As a bonus, both the carafe and its lid are top-rack dishwasher-safe.