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Discussion Starter #1
Hi Guys,

I'm only getting around 29-31 mpg from a full tank (CRD). Considering most of my miles are over a long distance with many A roads and motorways I expected more, I am planning to get the car maped next month but is there something else it could be.

I'm not really a fast driver just sit at 70 ish on the roads. The best I have ever had is 34mpg and that took a fair bit of effort.

Ta

Pants
 

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my crd is a little heavy at the mo and only average 30 mpg around town and little runs out ,have to sit at 56mph and just touch the throttle to get better ,but do find car needs a good 30min warm up to start getting better mpg
 

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It depends on how people decide what consumption they're getting anyway. Reading the mpg from the EVIC means nothing unless its only used for a comparison. The only way to decide your mpg is to calculate it by brimming the tank and then brimming it again and carrying out the calculations.

I always calculate mine, and get about 29mpg average.

Jack
 

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This may be the stuff of legends but I get between 33 - 38, mainly motorway and not hanging about. I normally expect 35 on the EVIC which is pretty accurate. The car does 30k a year and mpg only varies otherwise due to air temp ( drops a lot below freezing )

SL
 

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I've got to ease up on the old right foot by the looks of it!! Although I can get 38 on the motorway at a steady 70. Its just round town it suffers.......a lot :)
 

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The car does 30k a year and mpg only varies otherwise due to air temp ( drops a lot below freezing )
I'm a bit puzzled by this. Engine efficiency should increase with reducing air intake temperature. Cold air is denser than warm air and hence will provide a greater mass of oxygen for cylinder charge. This is why an intercooler is used to counteract the effect of turbo adiabatic heating. Perhaps there is another factor involved; eg cold tyres with insufficient pressure? Or maybe one or more of the engine sensors may be out of calibration; eg air temp, coolant temp, mass air flow, manifold absolute pressure? I can't say that I've noticed any seasonal mpg variations of any significance, but it would be interesting to hear what other owners can report.
 

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I thought (but could be wrong) that air is denser when cold so as such more fuel is burned. But that could be rubbish. The car is used 3 days a week for at least 60 miles at a time sonic theory the tyres would be up to normal temp over a prolonged journey. Today has been 2 x 150 mile journeys, mainly motorway some traffic and averaged 36 on EVIC.

Would be interested in any other reasons why the mpg drops in winter.

Cheers SL
 

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Yes, you are correct. Colder and denser air will contain more oxygen to burn more fuel. However, the resulting energy transferred to the piston and crankshaft will be greater than that achieved with warmer air. The increased efficiency comes from how this extra energy is exploited, eg by reduction of rpm through gearing, to maintain a desired speed. So there is also the efficiency of the auto transmission to consider. One thing I have noticed, in any season, is a noticeable improvement in mpg when engaging cruise control and which I attribute to the ECU doing a much better job than my right foot.
 

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I noticed a drop of about 2-3mpg on my Hemi recently. Rolling the car around the garage, it seems I have a mildly sticking - but not noisy and not notably affecting performance normally - brake, either parking or caliper. If it's a drop you've noticed, it's worth checking tyre pressures and brake resistance...
 

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On your cold weather question I've usually put that down to:
1. Electrics working harder.
2. Longer on cold start.
3. Longer for the engine to warm up, same for oil in the gearbox.
4. Similar for tyres.
My CRD does 1-2 mpg less on my regular journey but the same on a long 50 miles plus.
 

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I agree that the colder intake temps should make the car run more efficient but the air is also more dense to drive through,drag etc, winter fuel is not very good for economy due to anti waxing additives for cold weather. as for the brakes even a very slightly dragging brake will decrease mpgs a lot as I found out and the particular wheel dosent get warmer than the rest so hard to pinpoint, change the air filter every year too as this made a difference for me not Chryslers recommended interval. also dragging parking brakes are a contributor so make sure they are well lubricaded and free for all the components to move freely and adjusted properly.
 

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took a trip to Edinburgh two weeks ago.

210 miles each way....40 miles on moorland A roads and 170 on motorway

obviously variable speeds on A roads and steady 70mph on the A1....far too many speed cameras to risk going faster.

average 37mpg on the EVIC....havent calculated actual..

town driving i get average 23mpg.
 

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I noticed a drop of about 2-3mpg on my Hemi recently. Rolling the car around the garage, it seems I have a mildly sticking - but not noisy and not notably affecting performance normally - brake, either parking or caliper. If it's a drop you've noticed, it's worth checking tyre pressures and brake resistance...
Agreed. My sticky callipers decimated the mpg on mine
 

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The motoring organisations regularly say that the biggest factors affecting fuel consumption are driving style, tyre pressures and weight in/on the vehicle. Smooth acceleration and deceleration, planning ahead to minimise the use of brakes will give better figures. As will the correct tyre size and pressure. Keeping the vehicle as light as possible, even to the point of fuel level (say never fill up above half tank), and remove roof racks/bars when not in use and empty the boot of junk you don't need to carry. But to be fair, if you want 60+ mpg, get a Prius. If you want to enjoy your driving experience get a 300C.

Sent from AutoGuide.com Free App
 

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Discussion Starter #19
Lol @ the prius, going to get the garage to check the calipers when it goes in to the Garage on Tuesday just in case. My parking brake doesnt work for shit could this also be part of the problem I wonder?
 

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search parking brake on the forum here and you'll find lots of posts of them being all seized up!
 
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