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Discussion Starter · #1 ·
Hendry, I did a little experiment for you. On a nice long flat section of motorway this morning I set cruise control to 70mph and ran for a mile in 5th and a mile in 6th.

In 5th rpm was 2750
In 6th rpm was 2250

In 5th mpg was 44mpg
In 6th mpg was 71mpg

Now before you think that sticking a 6spd will give you a 27mpg gain, remember that mine is a 1.4 turbo car so fuelling increases as turbo boosts more at higher rpm. A normally aspirated 1.4 would be getting better mpg than my 44mpg at those revs.

Also remember that I'm running eco tyre pressures which means tyre diameter is slightly larger than running at light load settings which probably reduces rpm by a 100'ish at 70mph.

Even so, even in 5th my car is still doing less rpm's than your 5 speed box. It is one reason that I chose the 1.4T and 6spd combination as it is high geared for motorway cruising. Hence the reason it does not like being driven around town in 30mph limits because gear spacing is not right for lower speeds. The 1.4na and 5 speed felt much more comfortable in those low speed urban conditions.
 

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I'm running eco settings for the tyre pressures too (but the correct 39 front 37 rear, I seem to remember you saying you had yours slightly less than that)

250rpm isnt a huge difference between the 2 engines/boxes in 5th at 70, because when you mentioned in the other topic 80mph in 6th was only 2800 rpm I thought at 70 in 5th yours would be a LOT lower than 2750 so in that sense the difference isn't as big as I expected.
 

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Discussion Starter · #3 ·
Yeah, I run my fronts at 37psi and rears at 34psi. I found the cars handling and ride quality was not good with rears at the eco setting. 95% of the time I don't carry rear seat passengers so it was too firm and easily unsettled over our rough rural lanes.

The graduations on the rev counter are really difficult to read. Today I studied them very closely to get it accurate. The rpm figure quoted the other day at 80mph was approximate. I will double check that next time I get a chance although it was up around 3/4 of the way between 2K and 3K so won't be far off 2700-2800rpm.
 
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