Super unleaded, again, long and hardly worth it.

[ggthack@swansea.ac.uk (Graham Thackrah)]

I have mentioned this before but superunleaded does seem to make a difference
to the running of my engine compared to four star.

I am not about to claim that this is definately due to the fuel as the 
performance of my car seems to vary from day to day with no fuel being put in 
inbetween times, albeit slightly. Friends however, one with an identical car 
with mileage within 1k of mine also says that my car is noticeably quicker than
his. I know that I probably look after mine better than his with far more 
regular oil, filter and air filter changes and in the course of 118k miles cars 
are unlikely to wear similarly as maintenance varies between owners. However I 
still reckon that I can tell the difference between four star and unleaded if
filling up with the former after the latter on a relatively empty tank. Even
with the extra weight of the fuel, it runs better (quicker to rev when blipping 
the throttle between shifts) and needs slightly less throttle when cruising.

I would be more than willing to come along to a quattro club meeting (I have 
been meaning to pluck up the courage to turn up in my grubby 80) and try and 
convince anyone who is doubtful that it makes a meaningful difference. Or,
alternatively, come for a spin in a quattro while the owner tries it for 
themselves (is this a thinly veiled attempt at conning a lift in a quattro,
probably!). I hadn't thought whether an engine in bad condition would benefit 
more than one in good, or a four normally aspirated more than a five turbo, I 
shouldn't think it would make much difference. What I won't challenge is the 
high price of the stuff, I treat myself every three or four tanks.

What I am unsure about is how a highly knock resistant fuel would give better 
engine performance than one of lower knock resistance, assuming that 
pre-ignition (pinking?) is not present with either fuel? Does it mean that you 
can have more advanced ignition timing with a low knock resistent fuel? If so,
would I be experiencing a small amount of pre-ignition with the lower rated 
fuel when compared to the higher one if my engine timing was set up to run with
a more knock resistant fuel?

Phew,

Graham.

85 80 sport.