DO NOT think you can, with some simple formula, compare fuel economy measured with the various agencies methods! Because fuel economy results in the "real world" are effected by so many variables (including the people measuring them) it just isn't a simple thing! Heck, I can't even find a "dummies guide to performing the tests required" for -any- of the various "standards" (the nice thing about standards is there are so many to choose from). Now you KNOW, each auto manufacturer will fine tune their car to be tested, to give the best result possible. Can you blame them? They exist to make cars people will buy. Fuel economy is supposed to be important to consumers. So they do their best to get a good number. Is this "cheating"? Probably not, unless they are reporting false and/or made up numbers. We all know at least one who has done that, maybe we know of more. At any rate, to try to get numbers people will see in real operation, the EPA test designers make the tests rather complex. Other agencies just don't appear to care if people will see the same numbers their test gives. Or maybe they do but just gave up. The tests require several, and sometimes many, different methods, with the results combined in complex ways. So, if the rating you see is, for example, EPA, you may compare to other EPA numbers -FROM THE SAME YEAR and method-. Comparing to "JC08" or some EU method will not work! Even with "corrections". Until I see G4 numbers compared to, for example, GIII numbers, measured using the same method, I'm going to ignore the results of comparisons. In other words, I DON'T think you can say the G4 is 4% better, or 10% better, because you may be comparing apples to oranges!
Due to some manufacturers fudging on their cars MPG projections and missing badly the EPA will start to clamp down on their 'self policing' advertised numbers and do the tests themselves. Now because of the VW scandal that is pretty much on the backburner as the VW thing is what the EPA and Carb are riveting their eyes on. $18 billion is no chump change as well as claw back of tax credits for states which issued them to owners which did not deserve them. Because it was a fraud owners will not be liable for those issued tax credits. No info on how the tests will be done but they are to be as "Real" as possibe under real actual conditions not a dyno or lab scenario. Definition of 'Real" will be interesting but on the whole it should be a service to the public so they can gauge a REAL MPG value.
One thing, vagaries of comparing generations aside: the more the test methods reflect the reality of day-to-day driving, the more manufacturers will be forced to deal with shortcomings they might otherwise ignore, if their cars are only submitted to more theoretical, ideal testing conditions.
There was talk of making a test track that would be used to test the vehicle and its best MPG attempts. The track would have hilly areas as well as smooth pavement and rough roads. Stop and go areas as well as good portions of a straightaway. Now the total length of this track was not talked about but I am sure it cannot be some 1 mile total length lol! Maybe 10 miles? I do not know..but anyways if and when such a test arena is constructed it should be quite interesting when and if it comes to fruition.
I believe Consumer Reports does the 'drive a loop' method. I haven't checked but I believe there method is consistent (except for weather/wind?) from year to year.
THAT brings up an interesting point...They should have the test on some COLD days as well a HOT days...can we then extrapolate those numbers and average them to be Autum and Spring? Just kidding but would be interesting..
funny thing, when i bought my '04, and filled up after my first full tank, i got 60 mpg calculated, dead on. and that was before i'd heard of priuschat, or pulse and glide. when the epa made them change the sticker to 50, i still got 60!
Your MPGs are great! I'm on my first tankfull and claims 48 mpg but wife filled hers up but calculated 38 mpg. Yeah my wife with the 09 and me with the 04 are just learning HOW to drive with economy in mind...not easy when the wife's other car is 03 Mustang GT Conv and mines the 2002 SS Camaro Conv...lol! But I admit it is fun. Lots to learn as to the driver habits. I think we have to get shoes outfitted with egg holders between gas pedal and shoe to maximize the MPG! SECOND THOUGHT.....I think yours is the one which the factory is still looking for!!!
The CR consistent driving around the loop apparently involved very fast stopping, as no regeneration is obvious in their results. The EU 'driving' test involves much more idling than the US EPA test, which favors engine start/stop. How much idling is the 'right' amount?
The Consumer Reports rating for Gen3 is like 30 MPG City ...might be consistent but other worldly. Very whacky. If they ever do get a better method, EPA should please use E10 like the rest of us have to.
CR doesn't post the acceleration and deceleration rates used during the test, so it likely depends on the driver. They don't test in the wet, but that still leaves the effect of wind, temperatures(the test track is in Connecticut), and the local gas station gas they use. There is simply too many variables for CR's MPG numbers to be comparable between models that weren't tested on the same day. It is easy to design for the test with the official ones, but there the only variable is the car. The onboard emission testing equipment that is used by the ICCT and other researchers have dropped in price. We will likely see the official lab testing done, since emission and fleet fuel economy regulations are tied to them, but real world testing may become required to confirm those results apply outside of the lab.
