In the United States, there are nearly 300 million registered vehicles on the road. And of that number, four million of them are Class 8 semi-trucks. That seems like a small number, especially considering how many semi-trucks you can count on a road trip. But what also might surprise you is how old the average car and semi-truck are.

The average age of cars and semi-trucks rises every year

The average age of cars on the road today is 12.1 years, which makes the median model year a car from 2009. This is according to CNBC, who utilized IHS Markit research. Meanwhile, the average age of Class 8 semi-truck was 12.8 years old in 2018 according to NTEA. While that’s not a huge age gap, this doesn’t account for every commercial vehicle on the road.

Class 6 vehicles, which can haul 19,501 to 26,000 lbs, are 16.5 years old on average. This includes vehicles like beverage trucks, rack trucks, and most significantly, school busses. Perhaps the most interesting statistic, however, is how the age gap has grown over time.

In 2008, the average age of a semi-truck was 11.2 for Class 8 semi-trucks and 15.7 for Class 6 heavy-duty trucks. But for cars in 2002, the average automobile was just 9.6 years old. So while the average age of semi-trucks has only gone up by a year, the average age of cars rose by three years. Part of the reason for this is simple: semi-trucks live longer lives.

Semi-trucks live a much longer life than cars in terms of mileage

On average, cars last 12 years, and semi-trucks last about 15 years. But while cars average 200,000 miles before they conk out, semi-trucks can last 500,000 or 750,000 on average. And there are plenty of trucks that exceed 4 million miles of service before they’re retired or scrapped.

But semi-trucks are built differently. Their diesel engines were designed to run forever, fitted with an average of 200 gallons of gas to make up for poor fuel economy. If the average fuel economy of a semi-truck is 6 miles per gallon, that’s still 1,200 miles per tank. That’s more than even the most economical gas and electric vehicles.

But the main reason the age of vehicles is rising for both cars and trucks is that prices are going up. And with Covid-19 and electric cars pushing people to hold onto their cars longer, those ages are sure to rise.

Why are average vehicle ages rising?

The average price of a new car is higher than ever, making most cars unobtainable. But that’s also the case with semi-trucks, which cost $165,000 on average. It’s a lot cheaper to keep an older fleet running than to invest in a brand new one.

The rapid transition to electric cars won’t help the average age either. Plenty of people are going to cling to their gas-powered vehicles as long as possible until electric cars become more mainstream. They might be in the news a lot, but that doesn’t mean everyone is buying them.

What we’re seeing is a rise in expensive cars, and people who can’t afford to buy them. So until prices regulate, for both gas and electric cars, chances are the average age of vehicles will continue to rise.

My advice? Hang onto your current car for a while.