"The Natural Philosopher" wrote in message
...
On 21/08/15 10:35, therustyone wrote:


The only time I've noticed a slightly smoother engine (though no
significant improvement in mpg) was when I accidently filled up
with premium diesel instead of standard diesel - and a lot of that
may have been wishful thinking to compensate for paying through the
nose for the "gold plated" fuel :-) I wouldn't have minded quite
so much but I'd driven past loads of garages on my journey, holding
out for the cheapest garage that I happened to pass, and then when
I found a cheap garage I went and used the premium holster instead
of the standard one. Shame they aren't different colours (eg black
versus black with yellow stripes, or something like that).

might depend on the car's sophistication. A quality engine will
monitor pinking and adjust the timing and fuel ratio to optimise
burning with the better quality (petrol anyway) it finds. An older
car will just be set to run on the worst fuel around.

However a car adjusted to run on low grade fuel either by fixed design or
automatically will still run better on better fuel.

The first diesel car i had, a Peugeot 306 with the 1.9 non-HDi engine, had a
tendency to hiccup slightly as I applied a small amount of power after
braking (ie when the accelerator had previously been fully off) and when
coming right off the power as I was about to brake. It was as if there was a
minimum amount of fuel that the engine could deliver, with a sudden cut-off
as you released the accelerator below this point and a sudden delivery of
fuel as you pressed the pedal, rather than smooth control right down to
zero.

It was this symptom which seemed to be better with premium diesel than
normal diesel. However it returned as soon as I filled up with normal diesel
again, so any cleaning additives in the premium had a very short-lived
effect. A bottle of injector-cleaning additive in the tank had a much more
long-lasting improvement on the symptom, which only returned several
thousand miles later.