When the 8-speed automatic was first announced for the 2015 Corvette Stingray, most of us saw the main benefit would be an increase in fuel economy and that has come true as the new paddle-shift auto gets an EPA-estimated 29 MPG on the highway But the new automatic is also faster than than the previous 6-speed with a 0-60 mph time at 3.7 seconds.
In fact, the 8-speed automatic-equipped 2015 Stingray is 0.1 seconds quicker than the previous 6-speed automatic with a quarter-mile time of 11.9 seconds compared with the 12.0 seconds in the 6-Speed auto.
The EPA estimate of 29 MPG is a 3.5 percent increase over the fuel economy of the previous 6-speed too. The new 8-Speed is rated at 16 MPG in the city and 20 MPG combined.
“The Corvette Stingray is a great example of how we are leveraging engineering and technology to improve both efficiency and performance,” said Mark Reuss, GM executive vice president, Global Product Development, Purchasing & Supply Chain. “No other car can match 460 horsepower, 0-60 mph in better than 3.7 seconds, and 29 mpg on the highway.”
GM achieves the better performance and efficiency with the 8L90 transmission primarily through its 7.0 overall gear ratio spread which gives the Stingray a more aggressive first gear ratio.
Non-Z51 Stingrays with the 8-speed auto have a new lower 2.41 rear axle which reduces engine rpms by 8 percent on the highway at 70 mph. Z51 Stingrays will continue to have a 2.73 rear axle ratio.
The Corvette Team tells us that they just barely missed reaching 30 MPG and Corvette Chief Engineer Tadge Jeuchter does believe that number will be attained in the future. But at 29 MPG, the Stingray gets better highway fuel economy than some of its sports car competitors and even tops some conventional cars with smaller engines:
- Porsche 911 Carrera (28 mpg)
- Audi R8 V-8 (20 mpg)
- Jaguar F-Type R (23 mpg)
- Nissan GT-R (23 mpg)
- Subaru Outback six-cylinder (27 mpg)
- Volkswagen Passat six-cylinder (28 mpg)
- Mercedes-Benz C350 coupe (28 mpg)
Developed in house and built in Toledo, Ohio, the new Hydra-Matic 8L90 was benchmarked for faster shifts. The controller analyzes and executes commands 160 times per second. GM says this translates into wide-open throttle upshifts that are up to eight-hundreds of a second quicker that the dual cluth transmission offered in the Porsche 911.
“The Corvette’s new eight-speed automatic delivers the comfort and drivability of a true automatic transmission, as well as lightning-fast shifts and the manual control that enhance the performance-driving experience,” said Kavoos Kaveh, global chief engineer for eight-speed automatic transmissions. “It was designed to enhance the driving experience, with performance on par with dual-clutch designs, but without sacrificing refinement.”
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The 2014 Corvette Stingray’s 6-Speed Automatic is Rated 16/28 MPG by the EPA