Mazda has been promising to offer a diesel engine in the United States for what feels like an entirety, but it’s looking like the wait wasn’t worth it.

According to figures released by the EPA, the 2.2-liter four-cylinder diesel engine will allow the 2018 CX-5 to return 28 mpg city, 31 mpg highway and 29 mpg combined.

That’s massively disappointing as the petrol-powered model is rated at 25 mpg city, 31 mpg highway and 28 mpg combined. In essence, moving up to the diesel engine will only net you 3 mpg city and 1 mpg combined.

The story is largely the same for the all-wheel drive variant as the diesel-powered CX-5 is rated at 27 mpg city, 30 mpg highway and 28 mpg combined. For comparison, the petrol model gets 26 mpg city, 30 mpg highway and 26 mpg combined.

Unfortunately, the situation only gets worse when you factor in fuel prices. The EPA estimates the standard CX-5 has an annual fuel cost of $1,500 (£1,169 / €1,301) but that number climbs to $1,650 (£1,286 / €1,432) for the diesel model. The difference between the all-wheel drive variants isn’t as bad as the EPA estimates drivers would only save $50 (£39 / €43) by sticking with the petrol engine.

One of the few other competing crossovers with a diesel engine is the Chevrolet Equinox. It has a 1.6-liter turbodiesel four-cylinder engine that allows the front-wheel drive model to return 28 mpg city, 39 mpg highway and 32 mpg combined. While both the CX-5 and Equinox diesel are rated at 28 mpg city, the Chevy is rated 8 mpg higher on the highway and 3 mpg better overall.

Mazda hasn’t said much about the CX-5 diesel since 2016 – when it was supposed to arrive in the 2017 CX-5 – and it appears we now know why.