Archives

Diesel Drivers Report Superior Real-World Fuel Efficiency. (http://www.dieselforum.org/newsarticle/article/666/1/)

http://www.cleanmpg.com/photos/data/501/2006_VW_New_Beetle_TDI.jpgChristopher Cashman - Diesel Technology Forum - Dec. 14, 2006

2006 VW New Beetle TDI - EPA rated 37/44 city highway. EPA “YourMPG” Data Reveal Diesel Vehicle Drivers Consistently Achieve Higher MPG Than Figures Displayed On Window Stickers.

WASHINGTON - Diesel-powered vehicles deliver more real-world miles per gallon than the numbers on new-car window stickers currently indicate, according to the U.S. Environmental Protection Agency’s “YourMPG” database. The findings were detailed in EPA’s “Final Technical Supporting Document” accompanying the agency’s new fuel economy labeling rule released Tuesday.

The “YourMPG” data, compiled by the Oak Ridge National Laboratory, includes 221 diesel drivers measuring their own fuel economy and providing their real-world MPG to an Internet database. EPA then compared this real-world data with the projected fuel economy calculations it requires for all new cars.

“As can be seen, diesels appear to perform the best with respect to their label fuel economy, outperforming the label by 4.3%,” the EPA technical support document said. Diesel was the only power source to see an increase in real-world MPG. Gasoline cars decreased by between 1.4%-1.7%, while hybrid owners saw their real-world mileage drop by over 8% compared to the current fuel economy label.

“It’s long been known that diesel is the most fuel-efficient internal combustion engine ever produced, typically providing 20-40% greater fuel-efficiency than other technologies,” said Allen Schaeffer, executive director of the Diesel Technology Forum. “These reports from real diesel drivers across the country reaffirm diesel’s superior fuel efficiency, and will help consumers make future buying decisions when the next generation of clean diesel vehicles arrives over the next several model years.”

Automakers have recently announced a number of new diesel product offerings, and consumers can expect to see more diesel options available in showrooms starting in 2008. During this month’s Los Angeles Auto Show, DaimlerChrysler and Volkswagen teamed together to produce clean diesel vehicles for their Chrysler, Mercedes-Benz, VW and Audi brands under the Bluetec label. In addition, BMW, Cummins, Honda, GM and Nissan all announced plans to bring new light-duty clean diesels to the U.S. market starting as early as 2008.

Good for the diesel guys for putting up such respectable numbers.

I think it has to do with the low end toruqe of the diesel engine. It goes well with the lead foot of most american drivers.

One thing I wonder is if a group of diesel owners was prompted by a website to go there and post their numbers. If they are above the norm it may have skewed results. The sample size is small so it is possible that a lot of them could have come from a single website.

At any rate. I'm sure a lot of us here are just drooling over diesels cleaning up their act and getting a hybrid option.

I own a 01 NB TDI Automatic trans, the milage was in the upper 40's to the lower 50's until the new ULS fuel arrived and has dropped to 45 consistantly I worry about the lubrication to the injection pump, My new TCH has never run under 40 and have gotten 46 a few times under ideal conditions, I am waiting for the new deisel electrics that may be making an appearance in 2010.:)

It's too soon to blame ULSD for mileage drop. Remember that it was not implemented until late fall and with autumns glorious colors comes extended warm up times-especially for our fuel sipping TDI's. Many people in warm climates saw a mileage increase. I can't wait for summer!

Andy

I think diesel is a real alternative to efficient vehiles but this sums the aritcle for me:
Than Figures Displayed On Window Stickers.
Which brings it all back to EPA testing error, not the cars themselves.

If one vehicle is rated by the EPA as 60MPG but delivers 50MPG real-world,
While another reasonably comparable car is rated 42 but delivers 45 real-world,
I don't get how the 45 is 20-40% more efficient.

I've been part of a real-mileage database primarily for diesel cars and while my CVT (auto) based car delivers among the best efficient diesel drivers, while the same AT diesels are significantly less efficient.

Hi Steve:

___The item we all have to concede is that no matter if the automobile in question is a diesel, hybrid, or non-hybrid/E85 gas fueled vehicle, they do achieve the City/Highway FE as tested in the various manufacturers labs and posted on their window stickers minus the 10% highway and 22% city offsets. This is while being driven through the EXACT same City/Highway schedule. Even though these precise test schedules do not match the real world reality for 95% of the driving public, it is an apple to apples comparison of one car to another. What real world FE is achieved while driving at higher speeds, w/ higher accel and decel rates, while using accessories and in colder temps is where the FE deltas appear between the EPA and ones automobile as well as between one car and another. From everything we know, once you punch up above 70 +, a low Cd based TDI w/ a stick can take out all but the Insight and maybe the CRX’s of old. With accessories, I have to give the diesel its due as well. The smaller ICE’s of the super mileage cars and hybrids are adversely affected more by A/C then a 1.9 or 2.0L + TDI. All except maybe the Prius I/II and possibly the HCH-II given the OEM electric A/C capabilities anyway? Running the mechanical in the HCH-II as well as in the Insight in particular and the HCH-I to a similar degree will kill them as well :(

___Good Luck

___Wayne

[QUOTE]I have to give the diesel its due as well. The smaller ICE

[QUOTE]I have to give the diesel its due as well. The smaller ICE

I have to give the diesel its due as well. The smaller ICE’s of the super mileage cars and hybrids are adversely affected more by A/C then a 1.9 or 2.0L + TDI. All except maybe the Prius I/II and possibly the HCH-II given the OEM electric A/C capabilities anyway? Running the mechanical in the HCH-II as well as in the Insight in particular and the HCH-I to a similar degree will kill them as well
Sorry, I'm not sure what happened there but I'll try again:

Hello Wayne, I'll have to respectfully disagree here...at least regarding the CVT based HCH compared to an AT equipped TDI.
I've always known my own car can do mid-upper 40's driven +70MPH but given your quote above took my own car to the test. Last night I locked CC in at 71-72MPH w/no accessories and after driving 47 miles said 48 on the dash.
Without resetting the trip meter set out again this afternoon...late and in a hurry... and switched on the AC. This time without the CC on rode 70-80MPH, probably averaged about 77MPH and after the 48 miles parked at 47MPG. Again, this is consistant to what I've already known about my own vehicle.

Given some dash error of about 2-3MPG it compares right on with the diesels.

There is also factors regarding CVT vs DSG vs regular AT and gearing ratios, but between the two cars, both seem a pretty good choice. I can't speak about the other vehicles you mentio. I haven't driven them, but I know you have many hours logged behind most of them.

Thanks-
Steve

221 Drivers? That's a very small focus group. And what about a control group?

Bad science I say!

Hi Steve:

___The EPA tests are not about your drive, my drive, or anyone else’s drive let alone setup. They are an exact driving schedule under very exacting circumstances that all non-EV highway legal based cars certified for use in the US have to have been driven through. The (2) current test schedules have the exact acceleration and deceleration rates, lengths and number of stops, temperature bands, door listed pressures, warm and cold soak starts and the accessories in off prescribed in the CFR. Every car with an EPA sticker on its window went through the tests and the FE received matches up quite well for that vehicle being driven through that exact test schedule w/ the offsets applied. I hate to defend the current EPA city/highway test which so many find to be useless but it is an apples to apples comparison test between vehicles in a somewhat non-standard driving environment today. This is why I find it so useful! Drive a relatively new 2004 - 2007 Prius II w/ the door rated pressures through the two tests and the numbers come up 60 city/51 highway +/- a max of maybe 3% w/ the current 10 and 22% offsets applied. Drive the LEV based 2004 HCH-I w/ a CVT w/ door rated pressures through that same test and its numbers of 48/47 city/highway after correction will appear as well. If all drivers were to drive the current EPA tests in their daily commute with the exact conditions and setup, they would achieve what the stickers say 97 + % of the time. Just because some do not drive with that slow an acceleration/deceleration rate(s) or drive w/ top speeds far higher or with far more idling time at stops or in traffic depending on one’s daily grind so as to not match up to the City/Highway test procedures is our problem, not the EPA’s. A counterpoint to this is that the upcoming 08 - 11 schedules (the EPA is still using the FTP75 and HWFET schedules as we see today) will include a cold temp and accessory use test on that same schedule + a high accel rate/decel rate/high speed schedule. It will then combine the results into a formula with a number of unique offsets to bring the New Car (08 – 11) and hopefully locking them down after 2011 - EPA stickers to show what 80 + % of the public will receive driving that car or truck for a year round average. The new formula’s outcome with the accessory use, cold temp and fast accel/high speed schedules are pretty slick in order to clearly state what the vast majority of the US driving public will achieve day in and day out. There will be outliers just as most here reading this post achieve day in and day out but for the vast majority, the FE numbers posted on the new car stickers will come very close to matching their own real world driving FE day in and day out year round.

___Good Luck

___Wayne

Thank you Wayne.
I am also very much looking forward to the new testing system, as it will (hopefully) give consumers a better informed choice. I believe it's been the sticker error which have created the famous "hype" quoted by the endless parade of articles...and not the vehicles themselves in most cases.

Of course I'm only number guessing here, but if someone sees a diesel with the new numbers and see it rated at 45MPG, and the comparable hybrid at 45MPG then perhaps hybrids won't be so bad.
Perhaps the "hype" aspect will be gone.