MPG Query - Expecting too much???

[TheArchitect]

I'm running two cars at the moment a Clio 182 and a Mazda 6 2.2 (175) diesel. I use the Mazda for work as I do about 30k for work most of which is spent on the motorway. However I only get around 42mpg on average. My Clio which I've had to use the last two days for work as the cam chain has stretched managed 37mpg.

Am I expecting too high an MPG for the Mazda? They've both the same power output give or take (circa 180bhp) yes the Mazda weighs more but surely its more aerodynamic! and it is a diesel!

Below are links to the fuel up records on fuely.

[RizzoTheRat]

What speed are you doing on the motorway? If I spend the majority of a journey cruising at 70ish on a motorway I'm rarely below 50mph in a 170bhp Octavia which I expect is a little lighter than the Mazda. 41's about as low as I ever get on a tank and I need to be doing a lot of short journeys in traffic to get that.

[Ren Esis]

I would expect anywhere between 40-50 is ok to be honest. My 530d gets 46MPG (real world calculated, not OBC) and that is doing pure motorway commuting mileage with perhaps a mile or so on each end of B roads.

All I do is keep the speed constant, plan my overtakes in advance, avoid unnecessary revs and watch my footwork (don't floor it in a high gear). Check your tyres too, you'd be surprised how much you lose if they're under-inflated.

If I put myself in 'drive miss daisy' mode I can achieve higher, but lack the patience do drive like this for the whole tank.

[anonymous-user]

eh? so a two cars, driven in broadly the same fashion, and one has used 25% less fuel than the other one. What did you want, a magic car?? Sounds like a pretty good improvement to me.

If you want better values, drive slower and less aggressively.

[TheArchitect]

I'm sat at a sensible speed less than 80mph majority of the time which is why I had been expecting more from the Mazda. It weighs in at 1575kg kerb weight. Guess its not that bad was more surprised how close a petrol engine can get to it. I guess its all too easy to read too much into the official figures these days. Ill have a look at adding a few PSI to the tyres and see if that helps much.

[ManiacGT]

Its even worse when you factor in diesel being more expensive. Sorry.

[Sensibleboy]

Stick to less than 80 mph with a constant speed and you'll do much better.

[james_gt3rs]

I'd expect a diesel to be much better than that, otherwise what's the point? My old (petrol) Micra did about 45mpg on a motorway trip and that was a short geared noisy way to get places.

[P-Jay]

james_gt3rs said:

I'd expect a diesel to be much better than that, otherwise what's the point? My old (petrol) Micra did about 45mpg on a motorway trip and that was a short geared noisy way to get places.

It's also tiny with and equally tiny engine and lightweight - at a constant speed, even if it's not ideally geared for it, it should be very economical.

As other have said, your mileage isn't bad - you have to look past the engine alone - your Mazda is bigger, heavier and can carry a lot more than your Renault.

My Seat Exeo can see an average of about 50mpg on a long enough run if I stick to 70-80, but even doing my daily 4 mile commute I'm getting real world 41mpg - of course the trip computer is a den or lies and misdirection as everyone knows and tells me I'm getting 41mpg...