Drive a steady state of MPH in top gear, level ground, note the MPG, then downshift it one gear down & manitain the same MPH,, watch the RPM go up & watch the MPG go down, simple enough.High RPMs = worse gas mileage.
O.K. I pick 20 mph, and a 2.56 axle with a '52 thru '64 six cyl. gearset tranny that has a 1.68 second ratio.
With 27" dia tires that means 637 rpm in high and 1071 rpm in second...by golly there are more rpm happening in second gear. Lessee that was..
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watch the RPM go up & watch the MPG go down, simple enough.High RPMs = worse gas mileage.
