The study is based on input from 17,012 buyers and lessees of 2011-13 model-year new vehicles "who used information gathered digitally during the shopping process."
Of the Gen Y automotive consumers who hop online during the buying process, 47 percent use smartphones -- the highest among any demographic, the study found.
"It is important for brands and websites to pay special attention to Gen Y buyers, as they are increasing in market share at the greatest rate among all new-vehicle buyers" and are now responsible for more than 20 percent of all retail sales, said Arianne Walker, senior director of automotive media and marketing at J.D. Power, in a statement.
"Additionally, the digital presence of the brand through mobile advertising and content across mobile-accessible sites and apps may be a great way to reach Gen Y buyers, since we see almost half use a smartphone during the shopping process."
While desktop and laptop computers are still the primary channels for research, J.D. Power says tablet and smartphone use has risen dramatically in the past year.
Tablet use rose 39 percent, while smartphone use rose 15 percent. And for the first time ever, tablet users surpassed smartphone users -- accounting for 25 percent of shoppers surveyed compared with 23 percent .
The study also found that 34 percent of online shoppers used several platforms -- tablets, smartphones, computers, game consoles -- for their research.
Nearly all Internet car shoppers, 98 percent, head to auto manufacturer Web sites. In contrast, 83 percent visit dealership Web sites; 80 percent visit third-party sites, and 7 percent consult social media.
Walker said: "As automotive Internet users continue to rely heavily on automotive manufacturer and third-party websites, an opportunity is created for sites to differentiate themselves further by providing engaging content and useful shopping tools that target consumers at each stage of the shopping process."