the v6 makes more power and torque than the 2.0 so it is able to run higher gearing wihtout struggling

the 2.0 needs 3.92 rotations of the propshaft to turn the rear wheels one rotation
the v6 needs only 3.62 rotations to turn the rear wheels one full rotation

the theory says that you will get better fuel economy yes, but at the loss of acceleration and potential top speed, but when i fitted a 3.14:1 diff to my sierra i was getting better acceleration than a more powerful car fitted with the 3.92 diff, in fact, his had 140 brake and mine only made 129 and his torque figure was higher than mine, but in a straight line, i was leaving him for the proverbial dust as we both came out of the last corner at silverstone him leading me in second gear, then we both accelerated and he shifted to 3rd then i shifted to 3rd, then he shifted to 4th and i was past him

he must have had 10 car lengths on me at the start of the straight and i must have had at least 20 car lengths on him at the end

as this picture shows, the straight can't be more than about 500 metres long



as for economy, on a cruise with the standard diff the best i ever got out of it was 132 miles from 8.08 litres of fuel but after the diff was fitted i never really took any dedicated readings