2018 GMC Terrain Diesel AWD
Thirty-four miles per gallon. That’s what we averaged over more than 1200 miles of mixed driving in the diesel 2018 GMC Terrain. As you can see, the Terrain is no tadpole-shaped, pint-size runabout. It is a “compact” SUV of substantial dimensions and—as tested here—equipped with all-wheel drive.
Granted, the all-wheel-drive system has the clever ability to reduce parasitic drive line losses by totally disengaging the rear axle when it’s not needed. But still. The diesel-powered Terrain surpassed its EPA combined fuel-economy estimate by 2 mpg as driven by us (which is to say, driven harder than most people would) and outpaced its EPA highway fuel-economy figure by 1 mpg on our 75-mph highway test loop, for a stellar 39 mpg. This is no anomaly. The Terrain’s mechanical twin, the Chevrolet Equinox diesel, scored the same 34-mpg average and managed a remarkable 43 mpg on our highway test.
Great Fuel Economy and… Great Fuel Economy
The rest of the GMC Terrain merely whelms us, the diesel powertrain included. While gasoline Terrains powered by either a 170-hp turbocharged 1.5-liter inline-four or a 252-hp turbocharged 2.0-liter use a new nine-speed automatic transmission, the diesel pairs with the older 6L45 six-speed auto. General Motors claims the diesel has so much torque to work with that more gears aren’t necessary, but that seems dubious. Although it is true that the 1.6-liter turbo-diesel four’s 240 lb-ft of torque is substantial (its 137 horsepower less so), the same engine is bolted to the newer nine-speed transmission in the Chevrolet Cruze diesel. And that combination does a better job of keeping the engine at lower revs, where it’s quieter and still makes good power.
The Terrain’s six-speed suffers from larger spacing between gear ratios relative to the nine-speed, which allows the engine to briefly rev beyond where it makes useful torque before upshifting. Acceleration suffers from a distinct stepped feel, as the engine’s thrust falls off momentarily before the transmission upshifts, at which point engine speeds drop back into the meatier part of the tachometer and thrust returns.
If this process doesn’t sound fast, it isn’t. The diesel Terrain is slower than a procrastinating sloth, reaching 60 mph in 9.7 seconds. We have yet to test a 1.5-liter Terrain, but an AWD Equinox with that engine required 8.9 seconds, while the 252-hp 2.0-liter Terrain AWD reached the same speed nearly three seconds quicker. The diesel engine also produces more classic diesel rattle than you’ll hear in the Cruze with the same engine, as that car’s nine-speed keeps the diesel’s revs lower.
It’s Got a Look, Maybe Not the Look
Need a handy guide for telling the difference between the GMC and its Chevy sibling? The Terrain is the blocky one, while the Equinox looks half-melted. Most of our staff prefers the Chevy. In any event, this generation of the Terrain is dimensionally smaller and significantly lighter than the previous model, which straddled the compact and mid-size segments and is now right-sized for the class.
Inside, the Terrain’s rectilinear design hides the subpar materials on the dashboard and door panels better than does the Equinox’s more ambitious, flowing look, but the uneven panel gaps are visible all the time, even in our test car’s black interior. There are plenty of cubbies and storage bins throughout, and although the front-seat cushions are a tad short for taller drivers, the back-seat cushion sits nice and high off the floor and marries to a comfortable backrest angle.
The secondary controls are laid out neatly in logical rows a short distance from the steering wheel. GMC’s latest IntelliLink touchscreen both looks good and functions well, aside from its key menu shortcuts—lined up at the bottom of the display—which need larger onscreen icons. And we still think the Terrain’s push-button/tab-pull mishmash of transmission controls is asinine. Sitting at the base of the dashboard, they’re a pretty far reach for the driver.
Once you’ve figured out the transmission and gotten underway, the Terrain steers, rides, and brakes competently. GM may still have problems designing and building car interiors that don’t look and feel cheap, but chassis tuning is its strong suit of late. The GMC rides with an expensive solidity, its suspension and stiff body shell soaking up road imperfections with no sacrifice to handling. In perfect concert with the diesel’s long-legged highway fuel economy, the steering tracks beautifully straight on the freeway and requires almost zero corrections at the wheel.
As with hybrids, you pay extra up front for a mileage bump as significant as the Terrain diesel’s. The diesel GMC starts at $32,595 in SLE guise (the diesel can’t be had on the lesser SL trim) with front-wheel drive. For roughly that amount of money, you could buy a fully loaded Mazda CX-5, Honda CR-V, or Toyota RAV4 hybrid. To match their equipment in the Terrain, you’ll need to step up a level to the SLT (the version tested here) for $35,195. Oh, and toss another $840 into the pot for the Driver Alert Package I (blind-spot monitoring and rear cross-traffic alert) and $495 for the Driver Alert Package II (low-speed automated emergency braking, forward-collision warning, lane-departure warning, lane-keeping assist, and automatic high-beam control). These features are standard on those three competitors.
We’re not done yet—all-wheel drive, as on our test car, tacks on another $1800; fitting navigation to the 8.0-inch infotainment screen costs $1180; the panoramic sunroof is another $1495; and any color other than white is an extra-cost option, in this case $395. While you could spend even more on the (gas-only) Terrain Denali, our diesel test car’s $41,400 total is still an awful lot of money for an overall quite average compact, GMC-badged SUV, no matter how great its fuel economy is.