Ever Increasing Fuel Consumption

[Hannibal]

Basically, I’ve had the car for 7 months now (‘55 vRS) I’ve done 6-7k in that time. The car was newly serviced when I had it, just had it’s 30k service.

Over the last 7 months, I’ve noticed the fuel consumption gradually worsening. All styles of driving are affected, from motorway slogs to the regular work run. Both the mpg trip computer thing (which I don’t trust and always overstates economy), and quite simply, the number of miles from a tank have been getting worse.

I used to get 475-500 miles to tank on everyday driving, I now get 375-400. Over the last 7 months I’ve used a mix of fuels, from premium diesel (with marginally better economy) to supermarket juice, both with and with out a shot of millers.

It’s not happened overnight, it’s a gradual drop off.

Any thoughts please??? I’m reasonably sure that my right foot hasn’t got any heavier, and my tyres are correctly inflated. I’m thinking maybe filters are getting dirty, small fuel line leak……….? I really haven’t got a clue as I have the mechanical ability of a 7 year old girl. (That’s perhaps a bit harsh on the 7 yr old girl)

Many thanks in advance for your suggestions.

[orbital]

hello hannibal,im not a mechanic myself but in normal driving i get about the 400mile mark out of a tank.hope that at least tells you your not alone!

[viewer]

Very likely that the air filter is showing its age. The recommended change is at 40K so it may well be on the original. A new one is under a tenner from Halfords. Most posters here agree that 40K is too long and 10K is more sensible. I changed to a cleansable Pipercross and clean it every 10K.

[George]

I normally get about 400ish miles on a tankful. Thats with a remap of 180bhp, but recently mine hasn,t been as good on fuel. last time i cleaned the air filter (green replacement), and it seemed better on fuel. So maybe change the air filter. Hope this is any help.
Must clean mine soon.

[Hannibal]

So it seems like a new filter is needed. Thanks folks.

PS. I know others get circa 400 miles from a tank, it's just that I used to get sooooo much more........

[Wardy]

Are you noticing the car produces any more smoke, or any other differences? Smoothness, willingness to rev etc?

Steve

[DavidY]

Originally Posted by Hannibal

It’s not happened overnight, it’s a gradual drop off.

I've always noticed a gradual worsening in fuel consumption as it gets colder, and it gets better again towards summer. Not sure why, or whether it's enough of an effect to explain the figures you see though.

[Wardy]

Denser, colder air at this time of year. Car throws in more fuel to make use of it. Car runs quicker, but uses more fuel

Steve

[Big Mikey]

400 miles from a full tank for me too.

[Hannibal]

Hey guys,

1. I wouldn't say there's any additional smoke, certainly not a noticeable amount anyway. On the smoothness front, It's possibly a little rougher when I start it up, but I put that down to cold mornings. Perhaps a little rougher at revs too, but I may well be imagining it. I really am graping at straws.

2. I don't think it's the cold weather effect/fuel/air mix. It's been dropping off since I had it in April and at first I thought it was heat soak due the the cough errrr "summer" cough we just had.

[vindaloo]

Service schedule states to replace the air filter at 40K!!! Which is a stupidly high number considering it a simple paper element. And costs next to nothing

Also, now we're into cold weather, the diesel on sale will be "winter diesel", which has less shove per bang than the normal stuff but resists waxing better.

Also, also, try doing the "Cage" mod. <Do a search and listen to Basil>

Also, also, also... Other things to consider... tyres, tyre pressures, wheel bearings, brakes, can all have a bearing <groan> on rolling resistance and hence economy.

J.

[MikeW]

I got worse fuel consumption in cold weather than warm weather.

[Maffu]

I normally get the 'beeeeeeep' around 360/370 miles. I probably could get it to 'beeeeeep' later, but life's too short...

[Wardy]

Originally Posted by MikeW

I got worse fuel consumption in cold weather than warm weather.

See my last reply

(post number 8)

Steve

[Mort]

I get less than 300 to a tank. So nerr!

Be happy, it could be worse. You could have my car.

[Wardy]

Good grief!

It does have other gears you know, higher than 1st and 2nd

Steve

[ap0gee]

On the filter front, I too agree 40k is far too long for an induction filter. I've posted this before, but this was my filter after just 15k:



My fuel consumptions a bit worse than normal, but I think that has more to do with the Dragon box I put on a few months back! Still >400 miles out of a tank, though!

Another consideration (that I may be wrong about) is that I'm sure someone mentioned on here that the 'recipe' for diesel changes when it gets a bit colder. Assuming this means less heavy fractions and more light fractions in the blend (to help prevent waxing), then the calorific value is going to drop slightly...

[flyingscot]

Originally Posted by Wardy

Denser, colder air at this time of year. Car throws in more fuel to make use of it. Car runs quicker, but uses more fuel

Steve

Indeed, they also change the fuel mixtures at this time of the year due to the colder weather. Fuel in a car in Scotland is different albeit related to that is say France.

[Mort]

Originally Posted by Wardy

Good grief!

It does have other gears you know, higher than 1st and 2nd

Steve

There's 2nd?!?

[Wardy]