My son and I drove my truck to a car show about 3 years ago. Drove it real easy and never got into the secondaries. It averaged 13mpg. 528 Hemi, 10.4-1 MP 614/598 solid cam, 10" TA convertor, 4.56 gears, 31" tall tires. I'd tuned the dual thermoquads so at cruise they were about 15.2-15.6 a/f ratio. The motor made 683ftlbs. of torque, very little throttle opening was required to keep it at 55-60mph.Dave