If the MPGs are being derived by using 10% ethenol fuel...and you're using a high-octane, non-ethenol blend, you're going to get better fuel economy.

First off, see if the posted EPA figures are "ethenol related" and if they are and you happen to be using a high-octane (92 or better) fuel with no ethenol added, you're getting the better mileage because of that and that alone.

I noticed a 2mpg difference in my 450SLC between 10% ethenol-blended and non-ethenol fuel fill-ups.

"Corn is Porn when it comes to the Benzs."

(My saying...use it at your leisure...)

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M. G. Burg
'10 - Dakota SXT - Daily Ride / ≈ 172.5K
.'76 - 450SLC - 107.024.12 / < .89.20 K
..'77 - 280E - 123.033.12 / > 128.20 K
...'67 - El Camino - 283ci / > 207.00 K
....'75 - Yamaha - 650XS / < 21.00 K
.....'87 - G20 Sportvan / > 206.00 K
......'85 - 4WINNS 160 I.O. / 140hp
.......'74 - Honda CT70 / Real 125
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“I didn’t really say everything I said.”
. . . . . . . . . . . . . . . . . . ~ Yogi Berra ~