Falling MPG any ideas?

facade

You might find that the oxygen sensor in the exhaust is gradually failing due to old age/contamination. Worth checking the emission figures.

JustinR1979

Modern lambda sensors should last 100'000 miles+, but I wouldn't rule it out
Coolant temp sensor or thermostat (as stated) could give a drop without noticing a difference in how it drives.
Is this a modern car with no temp gauge? Saying that they're often weighted so can be a few degrees out. Often they have to get very close to specified running temp to go into closed loop.

Norman_Castle

Ultrasonic wrote: »

Are you referring to the trip computer indicated mpg or the real mpg there?

The real mpg. The trip computer will adjust for tyre wear.

Norman_Castle

Mr_Mink wrote: »

The heater sadly has never been the quickest (I've always just attributed that to the poxy little three-pot engine in it). Is checking the coolant thermostat an easy enough job to do or am I better off sending the car to the garage for that to be checked?

Normal engine temperature is generally indicated as halfway on the gauge. With an faulty thermostat it may reach and maintain this or just below in city driving but drop noticeably when you speed up. Another possible indicator is a higher engine temperature while in traffic without the interior fan on.

Depending on the car thermostats can be very easy and cheap to replace

JustinR1979

Norman_Castle wrote: »

Depending on the car thermostats can be very easy and cheap to replace

My last car thermostat was £100 and took 3 attempts.
This was reading normal, but was running at 68C instead of 79C.


This car about £3 when euro's had a sale on!

captainawsome

Wheel alignment? How was the wear pattern on your old tyres?

Mr_Mink

Ok so done some of the suggested tests. So the brakes seems to be heating up evenly though I'm less suspicious of them since this has been an issue since before the brakes were changed anyway.

On the engine temperate front I only have an Engine Coolant gauge available, this rose within a couple of minutes to the halfway point (90 degress c) and remained there for the whole half hour drive I took home last night (including dual carriageways at 70mph). I'm not sure, is this the right engine temperature gauge to be going off? If not I don't have access to any other gauges.

The old tyres were worn evenly to my eyes.

Norman_Castle

Right gauge. Engine temperature sounds fine.

Slowly_does_it..

What petrol do you put in it every week? - I assume you use the same place - Asda, Tesco, Shell..

Any difference in performance?

Just looking for ideas!

alastairq

I suggest a combination of all the little things mentioned before, plus the fact that your driving style will have altered imperceptibly over the time you've been driving the car. You will have become more used to the vehicle.....initially you would have been perhaps a little more circumspect about how you operated the controls, etc....time and experience make changes....

Try making a conscious effort to drive in an economical manner, see what effect that has?

[You would have been doing so when the car was new to you, without realising it]