Diesel - different grades ?

leehal

I am aware of different qualities of petrol, does the same rule apply for diesels ?

Should I be hunting round for some better quality fuel to improve my MPG ?

BillScarab

There is a premium type of diesel. I once filled up with it by mistake. The difference it made ot the performance and fuel economy amazed me, it was absolutely no different whatsoever!

anewman

Some people swear by Millers Diesel sport 4 additive, but driving a petrol can't say I ever tried it.

AdrianHi

Most people who set out to properly measure the difference over at least 3 tank fulls and do so over consistent driving and weather conditions measure around a 5% to 7% improvement in mpg. The same people switching back to a regular fuel see mpg drop back again. Some people see no difference and cry "snake oil".
On a 47mpg diesel car the saving is around 2 to 3mpg.
The saving is usually about the same as the increase price so turns out cost neutral. Most people notice a slight improvement in smooth running and performance of their car.
Because BP Ultimate Diesel became too expensive (i.e. more than a 7% price premium over standard) I tried using Millers Diesel Sport 4 additive and maintained similar results to BP Ultimate Diesel for a 2.5% price premium. It works out as a saving of about £80 a year - not a lot in the context of total motoring costs.

I've done a fair bit of research on the reasons why some diesel fuels may be better than others and it comes largely down to the additives used before you take deliver of the fuel at the pump (all Euro diesel has some additives after the refining process) and the resulting cetane rating (a measure of how well the fuel burns).
55 is the highest useful rating, any higher is of no benefit. Cetane rating will vary by refinery and time of year (diesel is "winterised") but manufacturers talk in terms of guaranteed minimums.
Here are some guaranteed minimum figures that I know of:
Standard: 51
Shell Standard Diesel (used to be Diesel Extra): 53
Total Excellium: 53
BP Ultimate Diesel: 55
Shell V-Power Diesel: 55
Millers and similar additives boost the cetane rating of a diesel fuel by 4 points giving a minimum 55 for any European diesel fuel.
As Shell standard diesel is 53 and priced as a regular diesel, short of using additives yourself, this is the best value for money.
Lubricants and detergents are also present in these additives and premium fuels which give benefit over long term use.