[Doggie 1]

A while ago I had unexplained loss of economy, down from 1000+ kms from a tank to maybe 850 kms. It didn't matter what I did, same driving, same everything, but just worse economy.
I had the fuel filter replaced at the 30,000 km service but still couldn't get back to 1,000 km per tank.
I was using Caltex Vortex Premium diesel, same service station, etc.
Then one time I put BP diesel in it (not premium as still no premium supplies in W.A.).
It seemed to run smoother and quieter but I thought I must be imagining it. But on the first tank I got 900 kms, then on the next one almost 1,000, then 1,047 and on this latest one am already over 1,000 and is still showing 57 km to go.
As I said, this is on standard diesel as opposed to premium Caltex.
Does anyone know why this could be?

[Dazzler]

That's interesting Dave!!!

I alternate between Caltex and BP (both standard diesel - no premium here)

For a few thousand KMs before my last Service (and Fuel filter change) my economy deteriorated too but not by as much as yours...

It is now improving too (but last couple of tanks have been Caltex) 

Although I think BP is a better(cleaner) fuel 

[Doggie 1]

The theory is still working.
Filled up (with BP) after 1021 kms, showing still had 57 kms to empty.
I didn't have to try to hit the thousand whereas before it was a struggle to get close.
The car is booked in for its 45,000 km service on Monday.

[Dazzler]

Hi Dave.. I might swap to a diet of BP only for a while.. I'm sitting on 5.6 at the mo...

[Doggie 1]

Hi Dave.. I might swap to a diet of BP only for a while.. I'm sitting on 5.6 at the mo...

Hi Dazz, it would be interesting to see if it makes a difference to yours