More than 1 in 3 people say they always tip their drivers when using rideshare apps like Uber and Lyft — but that’s not often the case for millennials.

According to a recent survey of 600 riders across the US, young people are less likely to tip than Generation Xers.

Eighty-eight percent of millennials said they tip “at least sometimes,” compared to 92 percent of GenXers.

“Millennials are accustomed to the concept of the sharing economy, whereas the older generation may view companies such as Uber and Lyft as more traditional services, like taxis,” explained Val Gui, COO of Instamotor, which conducted the survey.

“Also, millennials tend to be early adopters and became users of these rideshare services in the days where tipping wasn’t even a feature in the app,” he told The Post.

Describing reasons they would tip, twelve percent said they would do so if they got free goodies from their driver, compared to 9 percent of GenXers.

The survey also found that women are more likely to tip than men in most cases — with 92 percent saying they always reward their drivers, compared to 85 percent of males.

In addition, researchers also asked rideshare users to give reasons why they would give drivers bad ratings.

“Unsafe driving” and “unprofessional behavior” were the top choices, followed by “having a smelly car” and “poor navigation.”

Nearly 7 in 10 riders said they rated their drivers “at least most of the time” and only 22 percent said they had to report them.

In this category, millennials are also more likely to tattle — with 26 percent filing a report in the past, compared to 17 percent of GenXers, according to Instamotor.

The online used-car marketplace regularly conducts surveys and has polled people across the country about a wide range of issues, including sexual harassment.

For their rideshare analysis, the company surveyed 600 frequent users — defined as people who use a service at least once per month — from cities across the US.

A spokesperson told The Post that the group included “a fairly equal split of male and female riders.”