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Discussion Starter #1
Hey guys, we have had the Mii FR 75bhp since May last year.

For a while I was getting approx 62mpg, mostly dual carriageway and a bit of town. For the past 3 months or so it has dropped to around 52mpg.

I did a similar long run, last year was around 64mpg and the same drive last week around 53mpg.

No change in the driving pattern at all. Probably changed around the 10,000 mile mark.

Anything that could be obvious here?

Thanks - Keith
 

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Hi Keith,
Mine's done almost exactly the same thing - it was reliably >60mpg, and then as soon as the weather turned it barely nudged 52mpg in a tail wind. The type of driving generally only made a few mpg difference (motorways/long drives fractionally better than town/back roads). The only thing that has coincided with this drop is using the AC/heating to keep the moisture down in the cabin. I finally managed a long drive without either last week - bingo, 61.5mpg again. So I would suspect the climate control as a first answer.
 

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Thanks for the reply. I've had the heating on but not the AC. Will drive to work and back today with the heating off and see what happens. Cheers!
 

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did the wife fill the boot with sacks of compost and not tell you?

also the outside temperature has a huge effect. When its cold outside, and you have the heater on the engine temperature will drop compared to a hot summers day and not be as efficient.
 

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Thanks for the reply. I've had the heating on but not the AC. Will drive to work and back today with the heating off and see what happens. Cheers!
Also worth checking your tyre pressures, especially with temperatures starting to warm up again. It won't account for the full drop, but underinflated tyres will have an effect on fuel efficiency and sometimes it's a combination of small things that fix the problem, rather than one big thing. This is a US site that explains the principle nicely (see the bit headed 'How Much Does Tire Pressure Affect Fuel Economy').
 

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This is counter initiative. Engines like cold dense air, they perform more efficiently. But, this is more than offset by the extra aerodynamic drag of driving through cold dense air. But 10mpg seems excessive!
 

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No change in the driving pattern at all. Probably changed around the 10,000 mile mark.
1st service was due at 10k. Have you had this done and where? Did fuel consumption increase after this?

It's possible a software update might be the cause. My wife's Mazda 2 diesel used to do over 70mpg and after a software update (emmisions fix) only does 60mpg. I keep thinking about getting it remapped but have never got round to it.

We have exactly the same car (Mii FR) which my son drives and according to the MFD says 48.7mpg average. When I occasionally drive it I get 55-60mpg so he must the one one booting it!

Maybe take it for a spirited drive and use the full rev range or to try a fuel additive and see if things improve afterwards.

Otherwise it's still under warranty, so see if you local Seat dealer is interested in helping.
 

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For unscientific reference only.

Borrowed the Mii FR back (sons college shut!) and drove 32 miles from home to Darlington (10 miles country roads, 17 miles Mway and 5 miles urban roads) and according to MFD showed 61.2mpg for the journey.

This was 1 up, driving at around relevant speed limits, 7 degrees, heater at 12 o'clock, light traffic, changing gear at about 2.5k revs, tyres at 30psi and driving normally! Car has just under 6000 miles on it.

Allowing for a 10% over reading gives me about 55 mpg which seems about right.

Quite enjoyed driving it again. Car was refined and happily cruised at 70mph. Only felt like it lacked a bit of power going up steep hills and suspension a bit crashy over cats eyes on Mway.

Hope you get it sorted.
 

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Good to know - thanks for that. My numbers are based on miles covered between fill-ups and the litres added, not the MFD, so I'm confident they're 'real'. Even so, does seem like we're getting similar values under similar conditions (and mine's got 10x the mileage on it). Good little cars!
 
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