Probably a stupid question 5th or 6th?

[Spud7]

I own a facelift diesel and have been trying a bit of an experiment whilst on the motorway.

At say 75mph (IF one were to drive that fast ) my car would appear, on a run of any distance, to be more economical in 5th rather than 6th gear.

If my experience is not unique, would that suggest that:

a) 6th is overgeared for the allowed limit on out motorways and,

B) As the motor is obviously revving somewhat higher but using less fuel at that speed, does that imply that it's obviously more efficient at say 2400rpm than 1900 ?

Just wondered on other peoples experiences or thoughts?

 

[vile]

Interesting Brian but i cant see how 5th gear driving at 70mph is more economical than 6th

 

[tbourner]

Agreed. Unless the power/torque required was significantly more in 6th gear, but I can't see the engine being under much more load compared to 5th at that steady speed. This means the injector duty cycle will be almost identical, so it's down to the same amount of fuel being put in each revolution - more revolutions means more fuel.

 

[edgeoftime]

Probably happier to be revving than labouring, mine don't like 40/50 in 5, much better when buzzing a bit.