Mpg

[swagger]

Just been on a journey, and found that using 5th gear i got better mpg rather than using 6th gear, it was mostly motorway miles, i was doing same speed both ways, how can this be, surely 6th gear is for cruising etc

[kebrina]

Can I hi-jack, and also ask what is the most efficient speed for motorway driving? (Automatic)

[Mirez]

MPG is massively open to contributing factors - there is no set "efficent" speed however generally the slower the better.

 

5th being more econonmical the 6th is entirely possible, I would hazzard a guess you were quite laden at the time? Again generally, the lower the RPM the less fuel is burnt in order to propel you forward which is why 6th is normally preferable to 5th.

 

Let's say "normally" you use 40% of the engines power to maintain 70 in 6th, as rolling resistance increases (weight, tyres, wind, etc etc) a point will be reached where the power required to maintain 70 in 6th gets closer to 80%, ie the engine is working hard to maintain the lower rev position - Changing to 5th up's the rev's but more importatly - available power, which is why sometimes 5th can be better then 6th.