Which EPA to use?

[PaleMelanesian]

The european tests (NEDC) are more forgiving than the new EPA test, and roughly comparable to the old EPA test. If we want equal comparisons, we should use the epa for new cars, the revised epa for old cars like mine, and a ~15% lowered adjustment for the euro ratings to roughly match the new epa.


2010 Prius (I converted the L/100km numbers into US mpg):
EPA: 51 city / 48 hwy / 50 combined
NEDC: 59 city / 62 hwy / 59 combined
EPA is 85% of NEDC.

2007 Prius (that has both old and new ratings):
Old EPA: 60 city / 51 hwy / 55 comb
New EPA: 48 city / 45 hwy / 46 comb
New EPA is 84% of old EPA.

VCAcarfueldata.org.uk - Search Results - Further Information
Model 1 Vehicle Characteristics
http://www.fueleconomy.gov/feg/compx...Field=Findacar

[Piwoslaw]

Originally Posted by PaleMelanesian

The european tests (NEDC) are more forgiving than the new EPA test, and roughly comparable to the old EPA test. If we want equal comparisons, we should use the epa for new cars, the revised epa for old cars like mine, and a ~15% lowered adjustment for the euro ratings to roughly match the new epa.

'Lowered adjustment' in this case means mpg, not l/100km, right? So lowering mpg by 15% = raising l/100km by 15%?

Maybe the garage could have an option that automatically calculates standard numbers depending on what type was entered? (This should go to the bottom of the to-do list, next to unit conversion.)

[euromodder]

Originally Posted by PaleMelanesian

The european tests (NEDC) are more forgiving than the new EPA test

More forgiving to the car manufacturers then, or in easier words: less realistic ?

EPA is 85% of NEDC.

I'd already be hypermiling


Thanks for calculating the differences.

[320touring]

Interesting stuff!

I reckon I'll work off the 31.7 MPG UK listed in the manual, and take the New Highway EPA as my baseline for this forum

[PaleMelanesian]

Originally Posted by Piwoslaw

'Lowered adjustment' in this case means mpg, not l/100km, right? So lowering mpg by 15% = raising l/100km by 15%?

Of course, that's correct. I apologize for overlooking that.

[PaleMelanesian]

Originally Posted by euromodder

More forgiving to the car manufacturers then, or in easier words: less realistic ?

I'd already be hypermiling

Thanks for calculating the differences.

I found the old epa tests to be pretty accurate for a reasonable driver - eg my wife. She's not a hypermiler, but she does realize there's a connection between the gas pedal and the gas pump.

[Piwoslaw]

Originally Posted by PaleMelanesian

I found the old epa tests to be pretty accurate for a reasonable driver - eg my wife. She's not a hypermiler, but she does realize there's a connection between the gas pedal and the gas pump.

Since, as you noticed, the old EPA is about the same as the NEDC, then NEDC should also be good for the average driver. My opinion is that it's pretty hard to stay within the NEDC numbers. I could barely beat them before I started aeromodding and got serious with hypermiling. Before then I was a relatively slow (only 10-20km over the speed limit, which is very slow here) self-educated ecodriver. I think that Euromodder will agree about how hard it is to beat NEDC figures. Everyone at the my local car forum has worse milage (?kilometerage?) than NECD, the few that have tried to do better gave up without extraordinary results.

Maybe the difference is between American and European driving? Different traffic, different roads, different climate, etc. I guess I'd have to drive my Peugeot around the US to really see if there is a difference.

[euromodder]

Originally Posted by Piwoslaw

Since, as you noticed, the old EPA is about the same as the NEDC, then NEDC should also be good for the average driver. My opinion is that it's pretty hard to stay within the NEDC numbers.

That's my opinion as well.
Reaching the claimed 5L/100 km (47mpg) has been rather hard, and improving upon that didn't come as easy as my fuel log here may make it appear to be.

I've always had decent mileage from my cars even in my wilder years.
I was already "eco-driving" (think hypermiling without coasting, P+G, or physical mods) and driving well below the posted motorway limit before joining up here and starting to use hypermiling tricks like coasting, weight reduction, ...

I could barely beat them before I started aeromodding and got serious with hypermiling.

Like you, I've needed hypermiling techniques to go beyond the official numbers.

[PaleMelanesian]

I wonder if the fact that both of your cars are diesel has any relevance here. Could the NEDC ratings be harder to beat with a diesel? Maybe the test is a "best-case" situation for diesels, more so than gas cars. We don't have many diesel cars here in the USA, so I can't really speak on epa-diesel ratings.

[euromodder]

Originally Posted by PaleMelanesian

I wonder if the fact that both of your cars are diesel has any relevance here.

I doubt it.
Few people do better than the official FE values for their cars, regardless of wether they use diesel or petrol engines.