Is diesel "All the same"?

bryanb

Has anyone done a comparison in mpg terms on diesel fuel from different suppliers? I am aware that different grades of diesel exist, but is that supplied by the major fuel companies "All the same"?

daveyjp

It's all to a British Standard. There are too many factors which affect mpg, not just fuel. I've used all types and mpg is similar whichever I use.

Pew_Pew_Pew_Lasers!

Its all the same, bar additives which supposedly help keep the engine clean (and which aren't really necessary if you look after your car).

mark_belfast

They are all the same, expensive!!!!:mad:

Alfrescodave

All fuel companies have an exchange supply agreement whereby Company A can pick up fuel from Company B Refinery and vice versa. Therefore the fuel at a Shell garage may have been supplied from an Esso Refinery. The only difference being that own brand additives are added wherever the fuel is obtained from.

bryanb

Anybody know if "Own brand additives" are intended to increase the cetane rating or to keep injectors clean etc? Or even both?

leehal

Member Adrianhi posted this answer in a similar thread which I started a couple of weeks ago :-

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.

bryanb

Thanks Leehal, some useful info there. I've been using Tesco diesel with Millers, I have noticed smoother running (than straight Tesco) but haven't checked consumption accurately. I guess I'll carry on the same. Thanks again BB

AdrianHi

bryanb wrote: »

Thanks Leehal, some useful info there. I've been using Tesco diesel with Millers, I have noticed smoother running (than straight Tesco) but haven't checked consumption accurately. I guess I'll carry on the same. Thanks again BB

I cannot fathom a logic to it, but whenever I put Tescos or Sainbury's diesel in I loose about 1-2 mpg, but since there is always a margin for error in calculations and a variety of other factors affecting fuel consumption it's difficult to be "scientifically" sure supermarket fuels are worse. In any case many diesel car drivers including me look for the best price on a branded fuel and add our Millers because we *think* they are not as good.

Some of the cetane figures in that earlier post come from enquiries I made with customer services at Shell for example and come from their technical experts.

Night-owl_6

Tesco petrol you seem to get 5 more miles - I dont know but seriously you do, the prem stuff

AdrianHi

Night-owl wrote: »

Tesco petrol you seem to get 5 more miles - I dont know but seriously you do, the prem stuff

Most modern petrol cars will self tune to a petrol with RON from 91 to 98. 98 will give best performance and possibly MPG. Tesco's 99 has had very good reviews.