Hyundai and EPA may be inflating MPG figures

[BHarvey]

Originally Posted by Gone

Facts are a hard reality.

83 2011 Elantra owners have filled up their cars 2095 times, have driven 618,714 miles, are averaging 30.7 mpg, thought they'd get something from 29/33/40, and apparently, based on the OP, are unhappy. (Hyundai Elantra MPG Reports | Fuelly)

A hard reality indeed.

Guess they think being in an econo box allows them to flat foot it all the time...

[MetroMPG]

FYI, Pop Mechanics recently ran a fuel economy test using the Elantra (and Ford Focus). You can decide for yourself how valid their test method was (described in the article).

They found that their Elantra was good for 47.6 mpg (US) @ 55 mph and 39.3 mpg (US) @ 70 mph on their highway run. In their city loop, they measured 34.1 mpg (US).

Recall city/hwy EPA ratings for the car are 29 / 40 mpg (US).



Source: Mileage Moment of Truth - We Put 40 Mpg Claims to the Test - Popular Mechanics

[Old Mechanic]

As the manufacturers extract better mileage out of their designs, it will become much more difficult to beat EPA figures by a significant margin without significantly lowering your average speed.

The wife's Kia Sorento with the GDI 2.4 is averaging about 26 on her local stop and go driving. It's rated at 32 highway. Her previous car, an 09 Nissan Rogue, was rated at 27 highway. She regularly averaged 28 MPG in the Rogue driving basically the same routes over the years and tens of thousands of miles.

The Sorento weighs 3800 pounds, about the same as a Murano, while the Rogue was about 500 pounds lighter.

Best ever mileage for me in her Rogue was 33 MPG. I haven't driven a back roads 55 MPH average trip in the Sorento, but I would bet the mileage would be about the same.

I have seen over 32 on the Interstate and we recently removed the roof rack cross braces. In traffic I have seen 35 MPG, exceptional mileage from a 3800# CUV. Not overall for a trip but for 15 miles.

Bottom line, it was easy for her to beat highway EPA in her local driving in the Rogue. Best I have ever done with the Sorento is about 29 MPG on a local route drive, which is just about the same as I would have done in the Rogue.

I think cold weather (and we have nothing but E10 here) have a more significant effect on the direct injection engine mileage, both the E10 and the cold weather. It will be interesting to see what happens in warmer weather, and the EPA should stop using E0 in any testing since it is getting to the point where that fuel is no longer available in most of the parts of the country anymore.

regards
Mech

[tjts1]

The reason they're squeezing such good MPG numbers out of all these new cars is because they're using the VVT to run the atkinson cycle at part load. They're able to switch back and forth between atkinson and otto cycle very quickly so the driver never notices a loss in throttle response and torque. Even the mustang is using this trick.

[cfg83]

tjts1 -

Originally Posted by tjts1

The reason they're squeezing such good MPG numbers out of all these new cars is because they're using the VVT to run the atkinson cycle at part load. They're able to switch back and forth between atkinson and otto cycle very quickly so the driver never notices a loss in throttle response and torque. Even the mustang is using this trick.

That's a cool detail to know. I will look for this detail in the literature.

CarloSW2

[tjts1]

Originally Posted by cfg83

tjts1 -



That's a cool detail to know. I will look for this detail in the literature.

CarloSW2

It didn't even occur to me until I read it in a Mustang article.

The Duratec 3.7 V-6 is actually what the engineers call a "mild Atkinson-cycle" engine, where the variable intake valve mechanism keeps the intake valve open much longer than in a standard engine for better mixing in the chamber, thus reduced pumping work and better fuel economy.

Read more: 2011 Ford Mustang 3.7L V6 Engine - Muscle Mustangs & Fast Fords

"Mild Atkinson cycle"

First, the vehicle uses what he calls "mild Atkinson Cycle" combustion, which simulates a compression stroke that's shorter than the power stroke by leaving valves open during part of that stroke. This slightly reduces the power needed to pump air, improving its efficiency.

The Atkinson Cycle engines fitted to full hybrids run very efficiently at high speeds, at the cost of producing very little torque at low speeds. The hybrid's electric motor, which produces maximum torque from 0 rpm, neatly complements this.

Without an electric motor, the 2011 Explorer's engine can't run a full Atkinson cycle, but even shaving fractions from its pumping losses raises the power it generates from the gasoline it burns.

http://www.greencarreports.com/news/...id-tech-tricks

[SentraSE-R]

We got a 2012 AT Elantra. Drove it 2300 miles all highway from Louisiana to California. First 1200 miles at the PSL (as high as 80 mph in west TX), averaged just ~36 mpg.

Last 1100 miles I aired the tires up to 51 psi and drove between 60 and 65 mph, and averaged something like 44.7 mpg.