Using more gears on a manual gear box to save fuel?

only if 6 th gear is higher overdrive.. Most 5 and 6 speeds have the same gear ratio in top gear.

While listening to my car radio this morning, I heard an advertisement for a new Lexus with an 8-speed automatic transmission, so it seems that some manufacturers ARE going to more gears in their transmissions.

The reason for the extra gears is not so much for better fuel economy, but better overall performance of the engine. Gasoline powered engines are most efficient within a specific RPM range or “Power Band”. When the engine has to work above or below that power band, it is less efficient. The more gears you have available, the easier it is for the car’s engine to stay within its preferred power band, for better performance, and for better economy.

I think it has more to do with cost and complexity without sufficient tradeoff.

That is, it will be more costly to produce a 6-geared transmission, and more complex to maintain/service. And for ‘normal’ user who don’t usually engage gears optimally anyway, the mileage difference achieved won’t justify the extra effort.

More gears doesn’t necessarily mean more efficient, it just makes it easier to keep the car in the peak of it’s powerband. My Acura RSX has 6-speeds but at highway speeds in 6th it sits at around 4000 RPM which is higher than a lot of cars.

They’ve come out with some cars now that have a CVT (continuously variable transmission) that effectively has infinite gears