--- In [email protected], "Colin Shepherd" <[EMAIL PROTECTED]> wrote: >
> > If I can digress slightly from the theme of this evenings symposium (aka Tom > Lehrer) I find that if I use the diesel from a certain major supermarket > that doesn't start with T,M or W I get a stench of burning rubber out of my > exhaust. I'd only had the car three weeks when the dealer took the rear > brakes apart as I'd complained about the stench. I run my Zafira on BP's > Ultimate diesel as the computer reckons that on a long run I get 10% better > mileage. It might be subjective but I reckon I get more oomph as well. > > > > Colin First of all it appears that EN590 diesel is not a single product, bu a variety, all different. I recently contacted Total-Exxon when I bought some diesel that smelt distinctly like white spirit and nothing like diesel. When I eventually got to someone who was willing to try to help she said just that "there are several different types of diesel" - not help full when you consider that filling station proprietors can make extra money by adding white spirit and other non- duty hydrocarbons to their bulk tank. Consumer direct assured me that they would investigate but I heard no more and now alerted I have found derv from Shell, BP & Morrisons all have a similar smell. So the smell is likely to be due to a different formulation or even how the residues behave in any particle trap or filter. Petrol & diesel are made up from a whole list of "sub-species" of hydrocarbons which between winter & summer and now I know between bulk deliveries and it is not at all unreasonable to expect extra refinery processes to produce a fuel with a higher calorific value than normal. That would lead to more heat during burning, more expansion of the gasses so more pressure on the piston forcing it down harder so you need less fuel to deliver the same power. This effect would probably be enhanced if the engine electronics were adaptive enough to take account of this. However this is theory and I note that when Shell introduced their "premium" fuel and thrust leaflets at me it proved impossible to obtain comparative specifications locally. My only concern is that if the extra money is more than compensated for by extra mileage, in your case it appears that the answer is probably yes as its a computer that is telling you and not some subjective assessment of performance. Tony Brooks
