Besting Highway MPG In A Luxury Diesel Sedan

Recently, we were able to get behind the wheel of a 2015 Mercedes-Benz E250 and do some real world mileage testing. Our week of seat time consisted of start-stop daily commuting on the streets and freeway of the L.A. suburbs. We also found the time for some steady state freeway and desert back road cruising as well.

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The E250 BlueTEC Sedan is powered by the reliable 2.1L I-4 diesel. This BlueTEC engine delivers 195 hp at 3,800 rpm and 369 lb-ft at 1,600-1,800 rpm. It’s capable of high performance and high mileage, with an EPA rating of 28/42.

From the rear, the E250, and all new E-class sedans, have a sleek, cat’s-eye look. The LED tail lamps look good, the trunk opens to the bumper deck for easy loading and the tailpipes are in the bumper valance.

The interior of the E250 is spacious, comfortable and well laid out. We found all the controls to be within easy reach and generally in a location we expected them to be. The seats were comfortable, even on the longest legs of our test program.

By most accounts, the Mercedes-Benz E-class sedan is considered to be in the Mid-Size Luxury class. Essentially, this means that it’s more upscale than entry-level four-door cars, with more bells and whistles, while being smaller in scale than a full-size sedan. By our count, there are seven sedans in this class, but only three that are currently available with a diesel engine.

The E250 has an impressive array of standard features, in keeping with it being a luxury class sedan.  A few of these on the safety side are radar-based autonomous braking, and cruise control that steers and brakes.

Of these three diesel-powered offerings, the MB E250 is the only one with a fuel-sipping 2.1L four-cylinder diesel. While not as powerful as the competitor’s V-6 oil burners on paper, we didn’t feel a lack of power when driving the E250. The smaller 2.1L engine allows the E250 to offer up an EPA rating that has a 2- to 4-gallon city advantage over the two diesel-powered competitors and a 4-mpg highway advantage over both. In fact, the E250 has come to the market with a best in class EPA rating of 28/42. The initial info released by Mercedes-Benz on the E250 estimated a highway mpg of 45 highway, and while the EPA downgraded this to only 42 hwy, we were able to get long stretches that showed 45 mpg or more on the flats.

The E250 has an impressive array of standard features, in keeping with it being a luxury class sedan. A few of these on the safety side are radar-based autonomous braking, and cruise control that steers and brakes. The autonomous braking kicks in above 5 mph and uses “multirange radar” to check your speed and distance in comparison to the vehicle in front of you. Get too close, and you’ll get an alert to brake; ignore it and the E250 will brake for you. Also, when in cruise, the Steering Assist feature will help to keep you in your lane, even around mild curves.

While the 2.1L BlueTEC diesel engine is small and easy on fuel, it’s more powerful than some V-8s on the road. The twin turbos act in unison to provide quick response at low speed and rpm, while still offering up top end power when the as the larger turbo comes into play.

The 2015 E250, and, we assume, all E-class sedans, feature an under-seat package tray for both front seats. We found these to be on the small side, for maps or sunglasses only. They were also a bother on long drives. This is because the back of our feet hit them when we pulled a foot back on long drives, trying to stretch a little.

Having pumps that are designate for diesel trucks only is becoming more common at your local fuel stations. While standard at truck stops, this is a new phenomenon at the corner fuel stop. Take care when looking to fuel your diesel car at these stations, as the larger nozzle will not fit your car’s fuel filler opening. The following are standard fuel nozzle sizes:
Gas nozzles (unleaded and E85): 3/4 ID and 13/16 OD
Car/light truck diesel nozzles: 15/16- and 1-inch OD
Large truck diesel nozzles: 1-Inch ID and 1-5/16 OD (This is for local corner stations with 1-inch fill signs and at most commercial truck fill stations.)

Here you see driver’s information center showing a spot mileage of just more than 51 mpg. On our drive, we filled often, checking mileage under different fixed conditions. This super-high mpg was quite common on sections that were flat or just slightly downhill while trekking across the back roads of the Mohave Desert. Our average highway mileage was lower, but still impressive and still slightly better than the 42 mpg highway that the EPA gives the E250.

The driver’s information center, in the center of the speedometer, can display how much your driving consists of acceleration, coasting and constant, or steady state driving. On our flat desert drive, we had mostly constant pedal action happening. The only way to get better mileage is to roll down hill.

The E250 sacrifices the spare tire for a DEF tank. This is the one real concern we have with this otherwise pleasing sedan. While the E250 has run-flat tires, we could not find this fact in the owner’s manual, even after much searching. In addition, a sticker on the DEF tank to this affect would have been nice too. The trunk has 12.9 cubic feet of cargo space for all E-class sedans.
Our main concern was that driving across the wide-open spaces of the American West often puts you miles away from both services and cell towers. When punctured, run-flats are only good for short distances, at reduced speeds. A flat on the back roads less traveled could result in a longer drive to a service station than a run-flat tire is designed for.

The interior of the E250 is modern and full of conveniences. After slipping into the quite-comfortable front seat, we immediately noticed the 14-way power adjustments, lumbar support and other comforts. Better still, the E250 has a three-position memory for the driver’s seat. This allows you to store your favorite settings for seat position as well as the steering column and side mirrors, for yourself and two other drivers.

Perhaps the one thing that bothered us the most was the lack of a spare tire, or rather the lack of notification of a spare tire. We found that the early owner’s manual neglected to state that the E250 came with all-season run-flat tires, as the DEF tank took up the space normally used for a spare tire in the gas-powered models. Admittedly, the sales brochure did cover this and we’re sure the dealer would too. On the upside, the 17-inch run-flats rode well.

Overall, we were quite pleased with the E250 for comfort, conveniences and most of all for the little fuel-sipping diesel. The EPA rating of 42 highway and a fuel capacity of 21.1 gallons means a highway range of well more than 800 miles. This is about the distance from Los Angeles to El Paso, Texas, or a third of the way across the USA.  DW

THE EPA and Mileage Ratings

The EPA rates mileage on cars and light trucks in three categories: city, highway and combined. The testing that gathers this information tends to favor gas-powered vehicle, and it’s not uncommon for owners of diesel vehicles to get better than the EPA numbers, especially when driving with a light foot. In addition, diesel engines tend to get better mileage after a break-in period. Since the EPA testing is done on a “new” vehicle, diesels are disadvantaged during testing. This is because they’re at their best after engine break-in.

The 2015 Mercedes-Benz E250 has an EPA rating of 28/42 mpg. To most of us, this would suggest an average of 35 mpg. However, the EPA average is rated at 33 mpg. It seems that the EPA feels that the average driver spends more time on city driving so they weight these numbers. The average mpg rating is based on 55 percent of the time in the city and 45 percent of the time on the highway. As a result, all EPA average city/highway mpg number ratings are rounded down. The spread between the two is rounded down by 2 mpg, when the difference is 1.5 mpg or greater. This is why the EPA average for the 2015 E250 is only 33 mpg. Go to www.FuelEconomy.gov for mileage numbers and comparisons.

E250 Clean Diesel Stats

2.1L I-4 Twin-Turbo
Power: 195 hp @ 3,800 rpm
Acceleration: 0-60 mph in 7.9 sec (Optional 4MATIC: 8.2 sec)
City fuel economy: 28 mpg (Optional 4MATIC: 27 mpg)
Highway fuel economy: 42 mpg (Optional 4MATIC: 38 mpg)

By most accounts, the Mercedes-Benz E-class sedan is considered to be in the Mid-Size Luxury class. Essentially, this means that it’s more upscale than entry-level four-door cars, with more bells and whistles, while being smaller in scale than the full-size sedan.