Dear Car Talk:

I have a 2019 Subaru Ascent that I like very much. It has slightly less than 22,000 miles. My question is, at that mileage, should the injectors need to be cleaned, or for that matter, need to have anything done to them? It runs well and the gas mileage is good, but I am getting pressure from the dealer to have a “fuel injector service” done for $300.

I had my last vehicle for 10 years and never touched the injectors. Call me curious. — Rod

You’re right to be curious, Rod. And resistant.

The short answer is no. Your fuel injectors shouldn’t need any kind of service at 22,000 miles. Nor should anything else on this engine. At 22,000 miles, unless there’s a performance issue, oil changes should be all that’s required. The car’s brand new. And if there is something wrong with the fuel injectors at 22,000 miles, it ought to be covered by the warranty, shouldn’t it?

I’m afraid your dealer is looking for what we call A.D.P. — Additional Dealer Profit. So I would go to Google Maps, get him directions to the nearest lake and suggest he drive there and jump in it.

Several decades ago, fuel injectors would get dirty after some tens of thousands of miles. And we had a big machine at the garage that we called the Wallet Vac. It was actually called the MotorVac.

The MotorVac would run a solution through the fuel system and clean out the dirty injectors and valves. And at one time, we probably used that machine three times a week.

But in recent decades — to address that problem — carmakers have worked closely with the gasoline companies to make what they call “top tier” fuel, which is super clean. It includes detergents, too. And we hardly ever see dirty fuel injectors on modern cars anymore.

So skip this unnecessary service, Rod. If you want to avoid confrontation, tell the dealer “I’ll think about it ... maybe next time.” And tell him the same thing next time, too.

Dear Car Talk:

My new, 2020 Chevy Malibu promised on Chevy’s website — and on its MSRP sticker — to get 29 miles per gallon in the city. It doesn’t. The best gas mileage I have even gotten for a tankful of gas was 24 mpg.

I’ve returned to the dealer three times. They say everything is running as it should and according to spec. They showed