Very bad petrol consumption, help.

[Getrag]

The other thread went off the record so please lets keep this on tract. Sorry mods...

Its taken a very noticable increase over the last 2 days. Now a couple of things have happened at the same time. The last 2 days have been the coldest yet, freezing each night and ive been driving in it. Peak boost has also went up by approximately 0.2bar (which i try to avoid).

Now is this just the ECU upping the fuel to match the denser air or is there anything else to worry about like O2 sensors or whatever?

Oh, and will an ECU reset be in order?

Thanks, G.

[colsoop]

Hi there im not technical in any way, but if it helps i always get worse fuel consumption when it is colder and i produce more boost as well :( , i dont think your theory is far off the mark.

[JohnA]

colder weather leads to denser air which has to be matched by more fuel, so yes, mpg will go down a bit.
But we're talking 5-10% here as a ballpark figure. Otherwise you may have a damaged oxygen sensor or something. Check the ECU for errorcodes if in doubt.

[Markie]

I have noticed this also.. Figuring I am getting APPROX 19 MPG at the moment, and thats not hammering it at all :(

Is this normal do you think for a BPU TT?

[JohnA]

BPU shouldn't make a difference during 'sedate' driving.
I haven't seen a lot of difference in mpg even during spirited driving either (compared to stock).

Some fuels are more oxygenated and/or have lower specific gravity than others, so you get less energy from a tank.

On older engines full of carbon deposits sometimes a bottle of silver STP 'total system cleaner' helps (just the silver one though!). But if it's got lots of blowby the carbon crap will come back.

If you let it idle for long periods (warming up, heavy traffic etc) then obviously mpg will be even worse.

I get low twenties during what I call 'mild' driving, mainly off-boost.