These days, most professional tests of travel mugs focus specifically on double-walled stainless-steel models. Experts say this type of travel mug is by far the best at keeping hot drinks hot and cold drinks cold, and they are also typically more durable than plastic. Stainless steel is also less likely to retain flavor, so you can remove all traces of coffee taste and odor if you want to use the mug for something else.
Travel mugs from Zojirushi earn more recommendations from our sources than any other brand. Zojirushi travel mugs come in many different styles, sizes, and colors, but the one that most often comes out on top in professional tests is the Zojirushi Stainless Mug SM-SA (Est. $30). Reviewers at TheSweethome.com say that out of the 60-stainless steel mugs they looked at and the 20 they subjected to hands-on testing, the SM-SA offers "the best balance of heat retention and versatility." It's available in three sizes – 12, 16, and 20 ounces – and four colors, from muted to bright.
In TheSweethome.com's test, as well as a second test at Cook's Illustrated, the SM-SA earns top marks for heat retention, keeping hot water at a reasonable drinking temperature for hours. Both publications also praise the mug's "foolproof" locking lid. It closes securely to keep the contents from spilling, no matter how you shake, drop, or bounce the mug around, yet it opens easily with the press of a button when you're ready to take a sip. TheSweethome.com also gives the mug high marks for durability. It survives several drops with no more than a few minor scuffs, and after nearly three years of "constant use," it holds its heat as well as ever. The SM-SA is slender and lightweight, and its Teflon-type coating makes it easy to clean.
Reviewers admit the Stainless Mug SM-SA has a few flaws, though they're fairly minor. The main one, according to professional testers, is that it actually holds heat too well, leaving coffee or tea too hot to drink for over an hour after brewing -- so it's best to let yours cool a bit before pouring it into the mug. Also, its narrow shape doesn't fit snugly into many car cup holders, and some reviewers at Amazon.com say the narrow mouth makes the mug harder to clean. You can't just stick it in the dishwasher, either, because like most stainless-steel mugs, it isn't dishwasher-safe. Finally, the mug's nonstick lining may raise safety concerns for some users, who fear that hot liquids could leach harmful chemicals out of the coating. However, most experts consider nonstick coatings safe as long as they aren't heated past 400°F. (See our report on skillets for more details.)
In TheSweethome.com's tests, the SM-SA just barely edged out another Zojirushi mug, the Zojirushi Stainless Mug SM-KHE (Est. $30). In most respects, this mug is nearly identical to the SM-SA; in fact, reviewers say you can hardly tell them apart unless you look at them side by side. Both have double-walled stainless-steel construction, a slim profile, and a 5-year warranty on their vacuum-insulating properties.
The SM-KHE actually does slightly better than the SM-SA in the temperature test, keeping coffee a few degrees warmer over an 8-hour period. However, the testers find that on a few small but significant points, the SM-KHE doesn't quite measure up to the SM-SA. It's a couple of ounces heavier (in equivalent sizes), and its lid has a bulkier design that's more likely to bump your nose when you drink or block your view as you drive. It's also not available in a 20-ounce size. On the plus side, for those who prefer to avoid the chemicals in Teflon, the SM-KHE doesn't have a nonstick coating. Instead, it has an electro-polished "SlickSteel" finish that helps keep it from retaining tastes and odors.
If the high price of the Zojirushi mugs puts you off, you can get solid performance at lower cost with the Contigo Autoseal West Loop Travel Mug (Est. $15). This mug's key feature is its cleverly designed locking lid, which earns high praise from both professionals and users. Like the Zojirushi lids, it completely prevents spills and drips but opens with the push of a button when you want to drink. The difference is that the second you release the button, the lid locks again – so even if the cup is knocked right out of your hand, it won't spill. The Contigo mug is also a better fit for most cup holders than the two Zojirushis.
In other respects, though, the Contigo Autoseal West Loop doesn't match the performance of its competitors. It's nowhere near as good at retaining heat; in TheSweethome.com's test, it loses nearly as much heat in two hours as the Zojirushi mugs do in eight. It's also not nearly as durable. In two separate professional tests, dropping the Contigo mug from a height caused the lid to blow out or shatter completely, spilling the contents everywhere. Users at Amazon.com also note problems with peeling paint, leakage around the seal, and a plasticky taste and smell that lingers even after repeated washings. This may be because the Contigo's plastic lid, unlike the Zojirushi's, can't be dismantled completely, making it harder to clean thoroughly.
Still, if on-the-go convenience is your top priority, the Contigo's convenient shape and push-button seal could make it the right travel mug for you. It's available in 16- and 20-ounce capacities, in a choice of eight colors.
For tea drinkers who want to brew their drink on the go, reviewers say the Zojirushi Stainless Mug with Tea Leaf Strainer SM-JTE (Est. $35) is the best choice. This mug has the same sturdy, well-insulated construction as Zojirushi's other stainless-steel travel mugs, but it also includes a special filter for brewing tea right in the vessel. You simply drop your loose tea leaves directly into the mug and add boiling water, then tuck the filter attachment into the top before screwing on the lid. As you drink, the filter catches the leaves before they reach your mouth, so all you get is clean, fresh-brewed tea.
In tests at Good Housekeeping, the SM-JTE does a great job of maintaining the temperature of both hot and cold drinks. It also survives being dropped from a height without denting, scratching, or chipping, and it doesn't leak or spill when shaken. Users at Amazon.com agree that it keeps tea hot, and they also say the mug's wide opening lets you get the full aroma of the tea as you sip.
However, reviewers agree that the SM-JTE isn't as convenient to use as an ordinary stainless-steel travel mug. Instead of just pushing a button to take a drink, you have to unscrew the lid completely and set it aside, which makes it difficult to use this mug while you're driving. Also, some users find that the design of the tea strainer isn't ideal because there's no good way to remove the tea leaves when the tea is done steeping. So this mug isn't perfect, but it offers the best combination of heat retention, durability, and ease of brewing we've seen in a tea-oriented travel mug.