Two weeks on the road, Summer 2011; A trip to the Midwest and back --
Grumpy just returned from a two week trek to the Midwest, via Montana, Idaho, Utah, Wyoming, Nebraska, Iowa, Minnesota, and South Dakota. Starting with a full tank in Renton WA, fuel stops were made in Missoula MT, Ogden UT, Rawlins WY, Grand Island NE, Des Moines IA, Chamberlain, Spearfish and Belle Fourche SD, again in Missoula MT and the final fill-up in Renton WA, and holding an average (cruise-control regulated) speed of 70 mph on the freeways and the posted* speed limits where 70 was not allowed, resulted in a surprising 32-plus miles per gallon for the 4,746 mile trip.
Why was 32 mpg surprising? Well, it contrasts significantly with the 29 mpg achieved last year when 65 mph and lower was still the honored limit. Was the higher speed actually more efficient? A plausible reason? Yes, considering the fact that this car [the Red Rocket] has a five-speed automatic transmission where the torque convertor is locked out at mild throttle settings above about 50 mph, with unlock and downshifting occurring sooner and at smaller throttle advances at lower speeds when hills or headwinds are encountered.
NO, I do not think the higher speed (70 compared to 65) affected the achieved mpg. In fact, three years ago, when "real" gasoline was generally available and the Grand Mother first imposed the 65 mpg speed limit on our Midwest travels, this same car surprised Grumpy with an overall trip average of 34.06 miles per gallon. And last year, still under the 65 mph limit, the Rocket made just 29 mpg.
This year Grumpy discovered an interesting fact, clearly labelled on the fuel pump, starting in Montana. Next to the "Regular Plus" button, "Contains [up to 10%] Ethanol"; next to the "Regular" button, just a lower Octane rating. In Iowa, the "Regular Plus" was a lower price [enticing, but not to this wily old coot!] as well as a higher Octane. So Grumpy always chose the button selecting the grade of gasoline that was not labelled "Contains [up to 10%] Ethanol". Sure, I often paid a higher price (as much as $0.14 in Iowa), but I believe the higher overall miles per gallon more than justified this sometimes 5% higher price per gallon. You be the judge.
Also, it is a fact that, at higher altitudes the pressures in the combustion chamber cannot reach as a high a pressure as at lower altitudes; therefore it is reasonable that a lower Octane rating may be compatible with an engine, such as the Rocket's, rated for 87 Octane at sea level. At least Grumpy has not heard Rocket complaining about the 85 Octane that he selected in such places as Montana and Iowa.
As for me, I am convinced that from now on, I will watch for the subtle hint that will allow me to avoid Ethanol-laced gasoline in favor of the real stuff. I will be rewarded by a net improvement in economy by sometimes spending a little more at the gas pump.
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