That is right. EPA tests are done on a rolling dyno, and the highway test is done at an average speed of ~48mph. The result is than multiplied by some factor (something like 1.25) to reflect the "real life" conditions. The EPA tests are scheduled to be redisigned within a year or two (have been unchaged for almost 20 years).

Unlike Saabs that matches or exceeds the EPA highway numbers, most other cars do much worse. The main factor is transmission gearing - Saabs are geared for fuels efficiency at high speed, other cars are geared for performance. The 48mph test is unable to test this aspect. For example, at 48mph my Toyota Supra is already at its 5th gear at with ~2200RPM. It has no reserve to upshift at higher speed and underperforms its EPA number by about 20%. Saab 9-5 has 2200RPM at 70mph.

The quote below is from the attached link:

... The EPA is now weighing how to come up with more realistic estimates. Its figures are derived by putting every car on a dynamometer, sort of a treadmill for cars, and simulating a 7.5-mile urban drive at an average speed of about 20 miles per hour, along with a 10.2-mile highway drive averaging about 48 mph.

posted by 161.88.255...

http://www.usnews.com/usnews/culture/articles/040906/6diversions.htm

• Anyone changing to lower grade gas, due to high prices?, jimtimkim, Mon, 4 Apr 2005 10:10:17
  • Interesting web site for fuel MPG, BenL, Tue, 5 Apr 2005 04:39:05
    • Extremely biased and objective, dmz789, Tue, 5 Apr 2005 08:45:33
  • What? $3.29 for premium? Ouch, saw, Mon, 4 Apr 2005 19:00:57
    • thats still cheaper than here - usd$3.91 a gallon!, sab, Mon, 4 Apr 2005 19:29:26
  • Haven't ever used premium....., SaabHubby, Mon, 4 Apr 2005 16:07:02
  • It makes more economic sense to buy premium today, Dave in Houston, Mon, 4 Apr 2005 15:09:21
    • Re: It makes more economic sense to buy premium today, thor-in-2004, Mon, 4 Apr 2005 15:20:22
      • Viggen fillup = $40. Prius fillup = $20, Dave in Houston, Mon, 4 Apr 2005 16:48:07
  • When to buy Regular versus Premium?, thor-in-2004, Mon, 4 Apr 2005 14:53:58
    • Re: When to buy Regular versus Premium?, dmz789, Mon, 4 Apr 2005 19:04:30
    • Wow! All this just to divide two numbers? nm, dmz789, Mon, 4 Apr 2005 16:01:20
      • All what?, thor-in-2004, Mon, 4 Apr 2005 16:12:58
        • Re: All what?, dmz789, Mon, 4 Apr 2005 20:45:19
  • Yes. One of the best things about a Saab is that, Noel, Mon, 4 Apr 2005 12:53:22
  • Check your MPG, NonStop , Mon, 4 Apr 2005 12:46:33
    • I get better mileage with 87 vs. 93 (+), Vlad, Mon, 4 Apr 2005 13:55:50
    • MPG Improvement - Misleading, jimtimkim, Mon, 4 Apr 2005 13:35:20
      • Common wisdom misleading.., Mike Lynch , Mon, 4 Apr 2005 13:57:14
        • Perhaps... Findings on both sides, jimtimkim, Tue, 5 Apr 2005 04:31:24
        • Aero body kit? Less drag? my guess n/m, saw, Mon, 4 Apr 2005 19:03:59
          • Narrow rubber....anybody know the CD's...., Mike Lynch , Mon, 4 Apr 2005 20:40:07
          • Here is an interesting comparision, saw, Mon, 4 Apr 2005 19:48:21
            • Auto Aero is only 200HP n/m, TML , Tue, 5 Apr 2005 21:23:36
            • I might be wrong, but aren't the listed EPA numbers.., elliott, Mon, 4 Apr 2005 21:34:52
              • Re: I might be wrong, but aren't the listed EPA numbers.., dmz789, Tue, 5 Apr 2005 11:19:06 <-- Viewing This Message
    • Re: Check your MPG, TML , Mon, 4 Apr 2005 13:29:01
  • yep..n/m, niko, Mon, 4 Apr 2005 10:44:20
  • Why such a big difference in price from 87 to 93?, TheKillerPenguin, Mon, 4 Apr 2005 10:37:23
  • 91 is our highest in SF Bay Area, Scott Paterson , Mon, 4 Apr 2005 10:27:17

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