Enterprise Rent-A Car ranks highest in satisfaction among rental car companies for the second consecutive year, with a score of 831, a 26-point improvement from 2014, according to the J.D. Power 2015 North America Rental Car Satisfaction Study. Enterprise claims the top spot for the second consecutive year.

Enterprise Holdings’ other two brands rounded out the top 3: National ranks second with a score of 818, followed by Alamo with a score of 807. This reflected 21- and 31-point improvements, respectively, from 2014. After Alamo, Avis takes 4th place with a score of 795, followed by Hertz (794), Budget (785), Dollar (768) and Thrifty (733).

After plateauing in 2014, overall rental car satisfaction has reached its highest index score (798) since J.D. Power began its current methodology in 2006, according to the company. Last year, the overall satisfaction was at 774. Satisfaction is calculated on a 1,000-point scale.

The 2015 North America Rental Car Satisfaction Study is based on responses gathered from September 2014 through August 2015 from 12,101 business and leisure/personal customers who rented a vehicle at an airport location from August 2014 through August 2015.

Now in its 20th year, the study measures overall customer satisfaction with rental cars at airport locations by examining six factors (listed in order of importance): cost & fees; pick-up process; return process; rental car; shuttle bus/van; and reservation process.

In this year’s study, the greatest gains in satisfaction are realized in the shuttle bus/van (+37 points), cost & fees (+29) and pick-up process (+26) factors.

The study finds that 14% of customers have a problem during their rental car experience, up 1 percentage point from 2014. The most frequent problems are with the vehicle functionality, such as a dead battery or poor alignment, vehicle upkeep, pick-up process, staff service and billing, according to the study. Overall satisfaction drops 93 points to 717 when customers experience a problem — compared with 810 when they don’t experience any problems.

For business travel, customer satisfaction is 802, a 30-point improvement from 2014, while leisure/personal customer satisfaction is 796, up 22 points. This marked the first time under the current methodology business customer satisfaction surpasses that of leisure customers, according to the study.

Millennials are driving a surge in rental car customer satisfaction. Millennials have the highest level of satisfaction among the generational groups for both business travel (834) and leisure/personal travel (809). And they are the second largest group of renters overall (34%), behind Boomers (40%), and the second largest proportion of business travelers (39%), behind Gen X (43%), according to the study.

“Conventional wisdom says that millennials are perpetually dissatisfied, but that clearly is not the case,” said Rick Garlick, global travel and hospitality practice lead at J.D. Power. “Younger consumers are often more difficult to please, but as they get older—whether it’s because of maturity, experience, more income or all three — their satisfaction across many studies improves. We definitely see differences in the satisfaction of Gen Y consumers now that many are in their mid- to late 20s and 30s, compared with when they were in their late teens and early 20s.”

In addition to being the most satisfied generation in the study, millennial customers are the most likely to share their experiences via the Internet. Millennials who are delighted with their rental car experience (providing a rating of 10 on a 10-point scale) make an average of 5.83 positive recommendations. Yet when they’re disappointed (5 or lower), they make an average of only 1.46 negative comments about their experience, according to J.D. Power.

For more information on J.D. Power travel studies, visit www.jdpower.com/industry/travel.