My MPG has gone down??

Ultrasonic

tasticz wrote: »

I do get stuck in traffic but its always been like this car moves at 15-20mph at 30mph roads and i usually select high gear as possible to keep revs down.

Has the traffic possibly been worse since the weather has been worse? It has been for me and this could have a big impact on mpg.

(My above 50.5 mpg was due to a combination of wind, rain and heavy traffic.)

I wouldn't be rushing to check all your brakes myself just yet...

poppasmurf_bewdley

Where did you fill up your tank? I had the same problem with Morrisons diesel. My MPG dropped from the normal 43 to 36/37 with the Morrisons fuel. I left it until the tank was almost empty and filled up with Esso and I was back to my normal 43mpg.

tasticz

poppasmurf_bewdley wrote: »

Where did you fill up your tank? I had the same problem with Morrisons diesel. My MPG dropped from the normal 43 to 36/37 with the Morrisons fuel. I left it until the tank was almost empty and filled up with Esso and I was back to my normal 43mpg.

I will do the same as you did let the tank drain and fill it up all the way at sainsburys (I always get best mpg there for some reason)

When the light came on I filled at BP after the tank went half way I filled at JET and yesterday filled all the way to full tank at BP

Ultrasonic

tasticz wrote: »

I will do the same as you did let the tank drain and fill it up all the way at sainsburys (I always get best mpg there for some reason)

You said you'd been getting '35 mpg steady', now you're saying it varies?

tasticz wrote:

When the light came on I filled at BP after the tank went half way I filled at JET and yesterday filled all the way to full tank at BP

Phew! Hopefully that will stop this thread degenerating into a supermarket fuels are rubbish argument!

Weather and traffic are likely the cause, not fuel.

Did you see my question in post 9, regarding trip or tank average mpg?

tasticz

Ultrasonic wrote: »

You said you'd been getting '35 mpg steady', now you're saying it varies?

Phew! Hopefully that will stop this thread degenerating into a supermarket fuels are rubbish argument!

Weather and traffic are likely the cause, not fuel.

Did you see my question in post 9, regarding trip or tank average mpg?

yes because I have filled at sainsburys before this only couple times at the BP store and once before at JET when i say i get best mpg i meant in like compared to my friends best mpgs

i did see the post, the tank avg dropped to 29mpg as my car doesn't show mpg per trip

Ultrasonic

tasticz wrote: »

i did see the post, the tank avg dropped to 29mpg as my car doesn't show mpg per trip

And your last tank was about 35 mpg? Hmmm... that is quite a big drop then.

spacey2012

A poor thermostat could very easily be to blame.
Cars are built to run fuel rich when the engine is cold.

harveybobbles

If you're just taking the readout from the display then the last owner could have been a gentle driver and the mpg readout is slowly coming down to your actual driving.

Do the brim test to get the real world figure.

Ultrasonic

harveybobbles wrote: »

If you're just taking the readout from the display then the last owner could have been a gentle driver and the mpg readout is slowly coming down to your actual driving.

Are you certain that the trip computer mpg calcuation algorithm varies with driving style? I'm not. But either way the OP has owned the car for 6 months, and we're talking about a 17% drop in mpg between successive tanks so it's definitely not some sort of long term adjustment.

You are of course right that brim to brim measurements are the only way to be confident what the true mpg figure is though. Although the drop in indicated mpg is still likely to be significant.

bigjl

Ultrasonic wrote: »

You said you'd been getting '35 mpg steady', now you're saying it varies?



Phew! Hopefully that will stop this thread degenerating into a supermarket fuels are rubbish argument!

Weather and traffic are likely the cause, not fuel.

Did you see my question in post 9, regarding trip or tank average mpg?

In fairness to those that are happy to report genuine fuel economy differences it is normally diesel drivers that have noted an improvement when using name branded rather than supermarket fuels.

I would suggest that petrol vehicles are lot less complicated these days when compared to the average commonrail diesel.

But if you put supermarket into a highly tuned turbocharged petrol engine I suspect you will see a similar situation.

I know that you were advised by Subaru that performance would be neutered if you used lower octane petrol, but the engine WOULD STILL RUN, but the electronics would back everything off to protect the engine and turbo.

In the OP's position it could be just coincidence, but as the car is new to him perhaps an air filter and fuel filter change would put his mind at rest, perhaps a couple of tanks with some good quality injector cleaner may also help a little, as he ran the tank low there is a possibility of dirt that has long since been at the bottom of the tank getting dragged into the filter.

Either way changing the filters can only help in the long run.

If he has the facilities perhaps an oil and oil filter change to a known quality oil would help, don't know what car he has but a minimum of semi synth, though I personally usually use full synth, largely Castrol or Mobil though have used Comma and Valvoline Maxlife a couple of times. I tend to avoid no name oils like Halfords special, maybe to my detriment but that is just my policy.