Hi all

Just a quick one, only very recently my WRX has been using fuel at quite an increased rate although my driving style hasn't changed, always use V-Power. So far 40 miles has used a quarter of a tank, mixed between A roads and some minor town driving on the way to work, very rarely floor it on the journey...could something be at fault here or is it just because the weather is colder (told this by a friend)?

 

Yes

 

Have you tested your MPG before and after to get comparable results? Or are you just working from a "feeling"?

 

I can't see how the cold will make an engine use more fuel, might use a little more when it first starts from cold but once upto normal operating temperature there will be no change. I'm sure turbo's like sucking in cold air anyway

 

I'm going to work it out once I get through this tank, I always compare lol 28mpg normal average with mixed driving.

The journey to work is only 11 miles so I wonder if it isn't long enough :-s

 

Colder air is more dense and is seen as such when it passes the maf sensor. Therefore, more fuel is used to keep the air/fuel ratio in the right ball park.

So, yes, temperature is very dependant, up to 20% difference between winter and summer.

 

Could be a knackered lamba

 

If the thermostat is foobared the engine will run cooler. A cooler engine will guzzle more fuel as the coolant temperature sensor is the main sensor used for enriching the fuel mixture.

DO NOT rely on teh temp guage, the temerpature guage will still stay in the middle even if the engine is too cool as it has a dead band between approximately 70-100 degrees (i.e guage stays in the middle and doesn't move within this temperature range).

OBD live data will show the exact engine temperature. It should reach 88+ degrees in under 30mins and not budge afterwards. Regardless of driving style or heater setting.

 

Cheers for the replies fellas especially you Fat-Thomas

No engine management lights have popped up and all gauges are working fine, car doesn't feel any different either it is literally just an increase in consumption, will be having it serviced/mapped in the next couple of weeks so will ask the mechanic/mappers advice too

 

Weather has a really big effect on the fuel consumption of a petrol engine colder air is denser and needs more fuel or it would det it takes the car longer to warm up too plus drag from the wind, rain, snow, weight of the snow even my 1.6 petrol focus went from 37 to 30 mpg the scoob down from 22 to 16 ouch

 

Mine has dropped from 34ish to 30ish as temps get below 8c.

Is it just me or do cars always perform best when driven in temperatures what the car was mapped in?

 

That's just what happens in cold weather, there's a test here which shows a drop of 15% in MPG going from 18ºC to 2ºC.

 

Well I'll be dammed! Ha ha.

 

Thanks for clearing that up, thought I was losing it haha

 

not certain about your model year but classics used a water temp sensor buried under the inlet manifolds that only feeds the ecu not the temp gauge-if this goes off the engine stays in cold running mode-ie very rich and not much mpg-replacement is prolly about a tenner from a motor factors-can be swapped in situ on classics and I assume later models (if they run the same setup) but is a ball ache(22mm spanner IIRC)-ive done 2 both with good results.
As I say I'm not sure if it applies to your model year but worth checking
cheers richie

 

It's a 53 plate newage so not sure if the setup is the same