SUGAR HILL, N.H. — There are so many Subarus here in northern New Hampshire that people joke about it being the official state car. But the owners don’t joke about their fuel economy, which pretty much stinks.

This consumer displeasure has not escaped the attention of Subaru, which concedes that lackluster gas mileage has cost it sales. The company finally addressed the issue when it redesigned the midsize Legacy and Outback for 2010, and it has followed up by greatly improving the mileage of the redesigned 2012 Impreza compact.

The new Impreza sedan with an automatic transmission is rated at 36 miles per gallon on the highway, a whopping 38 percent increase from last year’s figure of 26 mpg. The city mileage estimate has jumped to 27 mpg, from 20 mpg, a leap of 35 percent.

The gains also make the Impreza the most fuel-efficient all-wheel-drive vehicle sold in the U.S.

I spent a week in a sedan with the continuously variable automatic transmission and Premium trim. The price — with a $3,000 option package that included alloy wheels, sunroof, navigation system and heated seats — was $23,545.

An automaker seeking to coax some small gains in fuel economy can typically come up with a few tweaks here and there. But to manage improvements of this magnitude it is necessary to spend some serious money for a new engine and transmission.

The variable transmission is a smaller version of the CVT in the Legacy and Outback. The unit responds promptly to the gas pedal, but during cruising it also lets the engine speed drop, improving fuel economy.

The other big change is a new 2-liter 4-cylinder engine, an offspring of Subaru’s first all-new engine family in two decades. It is a smaller version of a 2.5-liter power plant introduced in the Forester last year, and like other Subaru engines it is a horizontally opposed, or Boxer, design.

Subaru says the engine is more efficient and includes some lighter components because it was not designed to be turbocharged: some parts of a turbo engine have to be stronger to withstand additional pressure created by the turbocharger.

The new engine is rated at 148 horsepower at 6,200 revolutions per minute and 145 pound-feet of torque at 4,200 rpm. That’s a big drop from the 170-horse engine of last year, but Subaru says the new transmission’s quicker response helps make up for the loss of power. Also, the new Impreza weighs less — in the case of my test car, about 130 pounds.

Once up to speed, the Impreza is a fine companion for the driver in a hurry. The electric power steering’s consistent weight and feel are quite good — indeed, far superior to the steering in other recently redesigned Subarus like the Outback. With a reworked suspension and stronger body, the car responds quickly when the driver wants to change direction. Rumpled roads don’t upset either the Impreza’s handling or the comfort of its occupants.

I also briefly drove a hatchback and found the handling was similar. Subaru says it tried to make all the Imprezas ride and handle the same.

The new Impreza line does not, however, include new versions of the high-performance WRX and WRX STI models. Those cars got a makeover last year, though they continue to use the Impreza platform, and Subaru says it will be several years before new versions arrive.

Like all current Subarus, the Impreza has an all-wheel-drive system admired in snowy areas for its ever-ready competence. But the new sedan and hatchback are somewhat vulnerable in deep snow because of their carlike ground clearance of just 5.7 inches.

Subaru will remedy that deficiency in fall 2012 with an Impreza variant to be called the Subaru XV, which is to have 8.7 inches of ground clearance.

2012 Subaru Impreza

Base price: Sedan, $18,245; hatchback, $18,745

As tested: Sedan, $23,545

Type: Front-engine, all-wheel-drive compact sedan or hatchback

Engine: Four-cylinder, mated to five-speed manual transmission, for base models; 2-liter, four-cylinder with the variable automatic transmission

Mileage: 27 mpg city, 36 mpg highway