Increased consumption - stan
Over the past 3 months or so my car\'s fuel consumption has increased markedly. Average consumption used to be in the high fifties. Now it\'s about 50 mpg. The car is a Peugeot diesel (mileage 204,000) I can\'t detect a leak & my driving pattern hasn\'t altered. I suspect it\'s a symptom of a greater malaise,I\'m just not sure what though. Any ideas would be appreciated.

Increased consumption - Roger Jones
Can't recall what the temperatures were like before the three months started, but from my detailed records on the fuel consumption of two cars it is clear that ambient temperature does influence consumption, perhaps by up to 10%. That is, with exactly the same sort of usage all year round, fuel consumption increases in winter, and especially in January and February. The heating or A/C system undoubtedly has something to do with it, but presumably also the fact that the lump of metal in the front takes longer to warm up from lower ambient temperatures.
Increased consumption - Railroad
Cold air is more dense than warm air. Thus you get better volumetric efficiency on a colder day. That said, the engine will run cooler so that will probably cancel out any benefit. Short journeys on cold days will increase fuel consumption.

Tyre pressures, valve clearances, open windows, electrical loads, roof racks, etc, will all have an effect on fuel consumption also.

50mpg is still very good. I've got a 1994 Vauxhall Astra 1.7DTL with 176,000 miles on the clock and I get about 40mpg, 45mpg on a good run.
Increased consumption - Andrew-T
I have the opposite 'problem'. After 6000 miles/9 months at a steady 12-13 miles/litre, my 99T 306 HDI has decided to return 14 m/litre over the last four 20-litre fills (1120 miles). My driving habits have not altered as far as I know, but the oil is now Castrol 0/30 instead of Total (both semi-syn) and the fuel has had a few shots of Wurth common-rail conditioner. Has the turbo stopped working or something?
Increased consumption - Ben79
That may be the result of a higher spec oil.

My 1.4 Xsara economy reduced when I changed from Total 5W40 fully synthetic to a Total 10W40 semi synthetic.

If your car has only done 6000 miles in 9 months, it could have benefitted from the cleaner.

What is the total mileage of your car?

Ben
Increased consumption - Andrew-T
Ben - still only 26K - I got it last June at 18K, one owner, FSH (though that was pretty brief!) and in the colour I fancied. As far as I can judge from tyres, brake pads and pedal rubbers, the mileage is genuine, and the selling garage is in the Cheshire Trading Standards warranted mileage scheme. I assume it may have been a repo. car. Oil consumption is not measurable, probably less than 1 litre/20K miles.

When I got it the 'throttle' was sluggish, so I put it on a regime of regular shots of conditioner for a while, and took up the slack in the cable, which helped a good deal. None of it did much to the fuel consumption though, till recently - the change was quite sudden, noticeable and genuine.

 

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