If you’re interested in having a vehicle which is more stingy with gasoline, there’s some good news out this week. There’s also some terrible news. If that leaves you feeling a bit confused, don’t feel too bad because the reports coming out of the government can be more than a little bewildering. For one example which came out on Monday, the EPA said they were on track to meet the goals announced by the Obama administration in 2012. These CAFE standards call for auto manufacturers to produce fleets of vehicles which average 54.5 miles per gallon by 2025. Of course, that’s an average. If you produce some gas guzzling trucks, you’ll also need to sell hybrids to make up the difference.

But inside the same report, the EPA hedged their bets, saying that cheap gas will likely prompt more consumers to purchase bigger, less fuel efficient cars. And on top of that, the mileage standard really isn’t 54.5 miles per gallon anyway. (News 3 Las Vegas)

The U.S. government says the nation’s cars and trucks are well on their way to meeting fuel economy and emissions standards set for 2025, but cheaper gas prices could ultimately lower those targets by encouraging consumers to buy less-efficient vehicles… Under standards set in 2012, automakers’ fleets were expected to get an average of 54.5 miles per gallon by 2025. That’s not the real-world mileage vehicles will get; it includes credits for things like more efficient air conditioning systems. The real-world mileage is closer to 40 miles per gallon.

Okay… so it’s not really 54.5 mpg, but actually more like 40. But that’s still not too bad, right? Heck, when I was growing up, 20 mpg was closer to the norm. But is it really 40 mpg? It turns out that we have no idea because the testing standards that the EPA uses to determine fuel efficiency don’t work. The actual mileage of the vehicles can’t be determined using the tests which the agency mandates. A new report in Wired Magazine explains that the methods in place were established in the 1970s and they don’t approach real world standards.

Even if the car companies do, they don’t. Or at least, no one has any way to know if they do. Because the EPA’s test to make sure automakers are hitting their CAFE numbers—the sole federal, legal requirement that cars get more efficient—probably doesn’t work. At all… The mileage reported on those window stickers? Probably fine. But when it comes to CAFE, the system is bonkers. When the EPA tests for CAFE compliance, it still uses that laughable two-cycle system. It’s got no choice: The 1975 Energy Policy and Conservation Act specifies that “the Administrator shall use the same procedures for passenger automobiles the Administrator used for model year 1975.” In other words: When it comes to enforcing the only law the demands cars get better for consumers’ wallets and lungs, the EPA tests like your grandfather.

This isn’t the fault of the auto manufacturers, at least not entirely. They are following the test regimen mandated by the EPA. The mileage results are valid, assuming you drive like your grandparents did on a particularly cautious trip fifty years ago, but in real world conditions the results would be much lower. Also, as the report indicates, the computers which control every aspect of a car’s performance these days are undoubtedly tuned to produce a very attractive mileage number. But they only deliver those results under the specific conditions which exist when they are hooked up to the dynamometer for their mandatory testing. Those numbers go out the window when it’s under load. And that’s just the tricks they can pull without going the full fraud route like Volkswagen did.

The EPA is great at making up rules and issuing mandates. And if those result in some sets of numbers which look promising in a press release they can claim they are saving the environment. But in reality, they seem to have little idea what they’re doing nor any interest in nailing down the science. It’s mostly for show and scoring political points. So if you want to know what the actual mileage you’re getting from your car is, go back to keeping a notebook in your glove box, jotting down your mileage and how much gas you put in your car. Then you’ll have a real answer and it probably won’t be anywhere near what the EPA is telling you.