Everybody knows if you don’t pay to repair your car, you limit its life.

The same is true with people. We need medical care to avoid becoming clunkers.

For a half-century, Medicare has enabled seniors to get that care. But now the Obama administration is pressuring hospitals to skimp.

Last week, the administration announced the largest-ever change in how Medicare pays for care. It’s called “bundled payments,” and it’s the latest trick to squeeze care from seniors.

Bundling will make it financially risky for hospitals in New York and many other areas of the country to do hip and knee replacements. These two procedures have transformed the experience of aging, allowing seniors to stay active.

But President Obama says too many seniors are getting these operations.

When the subject of hip replacements came up in a 2009 town-hall meeting, he said “maybe you’re better off not having the surgery but taking the pain killer.”

Science proves the president is wrong. Seniors with severe arthritis who opt for a knee replacement are 50 percent more likely to still be alive seven years later than seniors who don’t. Pain and immobility are killers.

Medicare is moving from paying doctors and hospitals for each item and service they provide to the new bundling system in January 2016.

It’s being rolled out in New York City, Newark, Buffalo, New Haven and New London, Conn., and many other regions, including Los Angeles. About 100,000 seniors will feel the pain, one quarter of the number expected to get hip and knee replacements each year.

Hospitals in these areas will have to settle for a flat fee for all the care a knee- or hip-replacement patient might need — including surgery, pain killers, hospital stays, rehabilitation and home care — regardless of how things go.

If there are complications, the hospital and doctors lose out. Hospitals will have to cut corners, and avoid the costliest patients altogether. So if you’ve been considering getting a hip or knee replacement, do it before January.

Ezekiel Emanuel, the president’s health-care adviser, applauds the impending change, promising that “savings are immediate and guaranteed.” What savings? Not for you.

Bundled payments will force cuts in care, not necessarily “savings.” The new system will set up a conflict of interest between patients and the very people they need to trust.

Whatever the patient gets will come off the hospital’s bottom line and out of the doctors’ own pockets at the end of the year.

Seniors are guinea pigs in this new scheme. The RAND Corp. says there are no studies to show the impact on patients.

Isn’t that what health care is supposed to be about? RAND says the scheme risks putting “pressure on physicians to spend less time with patients or on hospitals to decrease amenities.”

Health-care analysts at Lewin Group predict hospitals will scrimp by sending patients directly home with only a part-time health aide instead of to full-time rehabilitation at a skilled nursing facility.

Another risk is that hospitals will use low-cost implants instead of allowing surgeons to opt for newer prostheses that give patients more range of movement.

Bundling payments is one of several ploys to shortchange seniors. In October 2012, Medicare began awarding bonus points to the hospitals that spend the least per senior, despite evidence that spending less results in higher death rates.

Americans know Medicare is running out of money.

But it’s better to have an honest conversation about how to extend its solvency, including raising the eligibility age and enlisting competition among private insurers, than to have the hidden incentives to cut care the Obama administration is using.

Rationing is invisible. Patients won’t know about the care they should have gotten or how much less they could have suffered.

Bundled payments, like other perverse incentives buried in ObamaCare, destroy Medicare as we’ve known it.

Betsy McCaughey is a senior fellow at the London Center for Policy Research and author of “Beating Obamacare.”