GMC has given the Acadia the biggest makeover in its 10-year history, shrinking the size and the price of its bestselling SUV while making it more fuel efficient and giving it new technology.

The 2017 Acadia's new base engine -- a 193-horsepower four-cylinder -- helps give the midsize SUV its best fuel economy ratings ever, at 21 mpg in city driving and 26 mpg on highways.

The Acadia's optional V-6 engine has also been revamped and now provides more horsepower and better fuel economy ratings of 18/25 mpg as measured by the U.S. government. The top government mileage ratings for the 2016 Acadia, which came only with a 281-horsepower V-6, were 15/22 mpg.

Last year's Acadia had six airbags, while the 2017 model has eight, including one that deploys between front-seat passengers to reduce injury in severe side crashes.

The new model also is the first Acadia with rear-passenger alert, which reminds drivers when they turn off the vehicle to not forget children or pets who might be in the two rows of back seats.

The federal government said the resized 2017 Acadia with all-wheel drive earned an overall five out of five stars in federal government crash tests. But the 2017 Acadia with front-wheel drive earned four stars overall.

Perhaps most notable for car shoppers is the new starting manufacturer's suggested retail price of $29,995. This is for a front-wheel drive, 2017 Acadia SL with four-cylinder engine and a six-speed automatic transmission. It is $1,905 less than the starting retail price for a 2016 Acadia.

The lowest starting retail price for a 2017 Acadia with all-wheel drive is $34,375 for an SLE-1 model with a four-cylinder engine.

The lowest-priced 2017 Acadia with the 310-horsepower V-6 is a starting MSRP, including destination charge, of $37,090 for an SLE-2 model.

Every Acadia includes standard three-zone automatic climate control; keyless remote entry; push-button start; rearview camera; Bluetooth hands-free phone connectivity; and a display screen that's at least 7 inches in size in the middle of the dashboard. And this year's Acadia is Android Auto and Apple CarPlay ready for the first time.

The Acadia was GMC's bestselling SUV in 2016, selling more than 88,000 units. But changes were needed to make it more competitive with popular mid-size SUVs that have three rows of seats, such as the Honda Pilot and Toyota Highlander.

The 2017 Acadia is 7.2 inches shorter, 3.5 inches narrower and 6.6 inches lower than last year's model, and it felt more manoeuvrable during a test drive of the top-of-the-line model, the Acadia Denali.

The size reduction means the cargo space behind the third row seats has been reduced by 47 per cent to 12.8 cubic feet, or about the size of a car trunk. But with second- and third-row seatbacks folded flat, the 2017 Acadia provides an SUV-like 79 cubic feet of hauling space.

The headroom remains the same in all but the third row, where the legroom has also been reduced, to 31.1 inches. These two rearmost seats are best suited to children.

The test-driven model came with the 3.6-litre, naturally aspirated V-6 engine, which powered the 4,000-pound SUV strongly for good startups and merging into traffic. Peak torque is 271 foot-pounds at 5,000 rpm.

Most of the test drive was on city and suburban streets, and it averaged just over 19 mpg for a travel range of 420 miles on a single tank of gasoline.

Note that towing capacity declined from 5,200 pounds in the 2016 Acadia to 4,000 pounds in the 2017 Acadia with a V-6.

The test-driven Acadia rode comfortably, with the optional-for-$1,200 variable damping chassis smoothing out bumps. The interior was quieter than expected.

The centre console storage area between the front seats was small, and real wood trim inside the Acadia Denali looked fake.

There was one safety recall of the new Acadia for brake calipers that might leak brake fluid and reduce stopping power.