Stooby,
In 1957, when I was a 13 year old kid, my parents bought a new 1957 Chevy station wagon equipped with a 265 engine and a "Turboglide" transmission. Even at age 13 that car was instantly recognizable as a future classic, the last of the "Shoebox" era. They had that car for about 10 years until it was hit by a drunk driver and badly damaged. The best fuel economy it ever got was about 14 MPG, and that was on good gasoline with no ethanol. The 265 was a very wimpy engine, way too weak for a family and camping gear.
I still remember having to get out and walk the last approximately 1/2 mile to a lake at elevation approximately 10,000 feet in the Sierra Nevada mountains in California. The wagon simply couldn't climb the last bit of that steep grade until a few hundred pounds were offloaded. That few hundred pounds was my friend and I.
Based on that I'd guess that a 265 can be counted on to deliver both poor fuel economy and weak performance.
