You don't have to be able to rev it out in every gear, a higher top would be good for steady motorway plods and mpg. I would benefit from a six speeder in my cinq, as it is, slightly modded, you can put it into the red in 5th - and a 90mph cruise sits you at 4800.
Most modern cars have an overdrive 5th or 6th, a Cavalier I used to have (1989 F reg 2.0 GLi) did 110mph at 3600 revs in 5th. Work that one out and it's geared for a theoretical max of 195mph. This didn't make 5th useless, just meant you were better dropping a cog or 2 for better acceleration. It'd do 40+ mpg on a steady 80mph run too.
Pete.
Cinq sporting 1242cc
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