MPG plummet - 2.4t 2001 v70 135K

[benja]

Hi,

mpg has always been around 28-31.

Recently needed new tyres on the front so I opted for winter tyres

now my mpg is at 26.5 and still dropping

Recently I had an issue where car was pulling to left, swapped tyres around and solved it, so I opted for winters on the front. there is possibility that the wishbones need replacing.

Any ideas? does cold weather have this much of an effect?

[Sojournermike]

Winter always has an effect, but how much seems a bit car dependent. I’ve usually been a couple of mpg off summer during winter months over the years.

[john.wigley]

I'm inclined to agree with 'Sojournermike', 'benja'. Has anything else changed apart from the tyres? Your normal MPG is similar to my own in a N/A auto car, which I believe is not untypical.

Short runs, ambient temperature, and many other factors can all have a bearing on fuel consumption. It might be stating the obvious, but if your MPG is continuing to fall, might you have a leak in the fuel system?

Regards. John.

[Georgeandkira]

Don't know.
Perhaps it's "posting a problem" website amplification effect but the Winter blends of fuel have come up a lot this year on all the boards I frequent.....or maybe your upstream oxygen sensor is gone?

[apersson850]

I've had the lambda sensor being faulty on my 854 Turbo once. The only thing I noticed was an increase in consumption from around 8 l/100 km to 17 l/100 km or so. About twice as much, but nothing else was obvious.
Error code "Fuel mix too rich" could be read.

But cold weather and no pre-heating of the engine does increase the consumption too. Not to double rate, though.

[benja]

Thankyou for replies.

only 2 error messages (bulb and alarm)

I'm pretty sure the tyres are the only thing that changed - my driving involves mostly short journeys but always has.

Quick note - i am going off trip comp only - i haven't yet done the pump calcs. but I'd say the rate the gauge is going down is in keeping with trip.

Would a leak in fuel system show on the trip comp? does it measure at fuel point of entry to engine or before?

[SandyVol]

This sounds like my v70, mine pulled to the left too and I saw a slow reduction in mpg. Turned out my front calliper was sticking.

Give it a drive then check the heat radiating off each wheel/brake. Is one noticeably hotter?

[benja]

Thanks for reply, brakes have been checked afaik. Will look again. A mechanic friend has suggested redex to clean the ejectors. So will do that and see if it changes anything.

[oragex]

At least here in Canada we switch to 'winter gasoline' in the cold season, which is believed to drop the mpg. Winter tires also have more adherence so that affects mileage a little.

Careful driving with winters only on front wheels, not to get too confident and speed past the rear tires adherence. Ask me how I know - loosing the rear end on the motorway is not exactly cool. Braking in a curve or downhill also needs attention.

[benja]

Just to update this thread.

Car settled at 26.3-26.6 mpg according to computer.

I tried redex to clean injectors, no perceptible difference to mpg.

I haven’t tried anything else but am putting it down to tyres.

Just going to live with it!

Ben