When new cars are approved for sale in the US, do the emissions standards take into account what MPG the vehicle will get, or is it based emissions/time or something else?
I’m starting to shop around for a new car, and I cringe every time I look at the estimated MPG for the cars out today. Other then a couple of hybrids, everything I’ve found gets worse fuel economy then the Honda CRX I owned 15 years ago. That include the tiny, light weight Smart fortwo. (3 cylinder, 1800lb car weight, and requires 91+ octane, so you get to pay more for the gas). The CRX was a heavier car with a bigger engine. What the heck?
I’ve wondered if the decrease in available MPG is due to current emissions standards, and if anyone has taken a look at the big picture. Are we actually putting more pollutants into the air, because fuel economy has gotten worse?
Vehicle emissions are measured at the tailpipe, with the vehicle generally at low-idle. This is how the guys who make the performance chips can get around the emission worries. The car tests fine at low speeds, but since nobody pays attention to how much the car spews out at high speeds, they don’t worry about how much gunk comes out of the tailpipe at 130 MPH.
New car emissions are dramatically lower than what they have been in years past. IIRC, even though a modern SUV gets worse mileage than a 1980s era car, it’s emissions are only a few percentage points of what the 80s make are.
One of the reasons you’re seeing worse fuel economy is that car makers are squeezing more horsepower out of smaller engines than they have in years past. If you don’t want to pay for a hybrid, and can afford to wait a bit longer, many car makers will be selling diesels starting with the 2009 model year, which will get the same or better MPG than hybrids for less money. You can read Popular Mechanics article about them here.
The EPA standards seem to be combination of emissions during idle and emissions per mile. It’s a little hard to tell exactly what their measuring and how just from the charts. One would expect that a vehicle that burns less fuel would also emit less…emissions.
(Ironically I used to write software for Ford that maintained a database of emissions performance testing and I can’t for the life of me remember any of this stuff.)
Mostly it’s because today’s North American car buyers don’t actually care about fuel economy, and are much more concerned with horsepower and features.
Uh, the most obvious answer is that the EPA changed the MPG calculation, and everything has taken a significant hit in “official” numbers. The mpg’s you see on new cars are closer to the real world driving conditions that you’ll experience. Only grannies ever got EPA mpg on older cars. Not to dig on your CRX, but neither of the Honda Civics I owned ever got close to the EPA sticker, for example, other than for long distance, speed-limit highway driving when the limit was 55 mpg.
YMMV (does that count as a pun?), but I got over 40mpg, and a friend that had the small engine version got close to 50. While neither of those are 55mpg, they are still a whole lot better then I can find in a similar car today.
This is not true. The EPA emissions test is done on a dyno in a simulated drive around Los Angeles called the LA loop.
Some states emission tests are done at low idle only, but the EPA tests done for certification are done at various loads, and engine RPMs.
Getting back to the OP. No mileage is not taken into account. Grams of pollutants per miles is what is measured. If you look at a new car price sticker (called a Monroney sticker) you will see a listing for the grams per mile of various pollutants.
The EPA did change how the calculation for MPG is done. This is to bring the numbers closer to what most people get in the real world.
::: Shrug:::
I have always been able to equal the highway MPG numbers on my cars. No one has ever accused me of driving like an old lady.