XSeries-forum

It may be coincidence but every time I fill-up if the diesel is frothy I never seem to get such good mpg.  It's not just on figures (which would suggest the tank not being completely full once the foam settles), but also on the OBC read-out.

For example, this last week I filled-up with very foamy Tesco fuel and over the course of 280 miles mixed driving never manged to get the OBC up 40mpg.  I filled the tank again with Jet which had barely any foam at all and within 20 miles I had 46mpg on the display (it did drop a bit over the course of the journey).  The journeys involved weren't identical but the distances, terrain, driving style, and average MPH weren't that different.  If anything the weather was colder/wetter when I got the better figures.  As per usual, the OBC and actual figures were within 1mpg of each other at the time of the re-fills.

Am I imagining it, or does less frothy diesel really give better mpg?  ...........Enough to make nearly 5mpg difference?

Discuss..........

It’s probably just different additives such as a higher detergent quantity in one of the fuels?  They all come from the same distribution depots regardless of what is on the side of the tanker.  Additives are the only real difference.

Could be one chain has switched to winter mix?

I have noticed that different temperatures result in either more foaming or less.

Air temperatures and humidity will affect what gets fed into the engine.  I have in the past noticed that there seems to be a sweet spot around 12°C that seems to result in a more lively performance.  Not doing many miles in mine (5k/yr) means the fuel stays in the tank longer so environment makes the change in how the car feels.  Performance ‘seems’ worse in very hot weather.  Ain’t temps out of the inter cooler that bit warmer perhaps?

I would go with the winter fuel as well.
The cold will make a difference as well but all will have the winter diesel soon i would think.