NEW YORK (MainStreet) – As consumers get more cost-conscious and the federal government implements new gas mileage standards, fuel efficiency has become a focus of every carmaker. And one way to get more miles per gallon is to make cars lighters.

Unfortunately, that means that many car companies are abandoning the once-standard practice of putting a spare tire in the trunk, says AAA, which notes that the combined weight of a tire, jack and tools can come to about 40 pounds. In its place are various alternatives, including standard “runflat” tires that deflate more slowly and kits that allow you to temporarily re-inflate and seal punctured tires.

The organization encourages drivers to read their owner’s manual and inspect their car to see whether the car is equipped with a spare – after all, you don’t want to find that out when you get a flat in the middle of nowhere. AAA also compiles a helpful list of cars built in the past few years that don’t come with spares (as well as what equipment they come with instead).

If you do have a spare tire, AAA recommends checking to be sure that it’s inflated and properly stowed. If not, you can either buy one of your own for around $150 (make sure to get a jack and lug wrench, too) or just rely on the inflator and sealant kit, which was hopefully included. As a final note, the organization recommends replacing the sealant every five years, as it can become less effective with age.

Matt Brownell is a staff reporter for MainStreet. You can reach him by email at matthew.brownell@thestreet.com, or follow him on Twitter @Brownellorama.