[A4] Need for Premium Gas in 1.8T quattro?

Brian White brian at bjwhite.net
Thu Sep 21 19:02:09 EDT 2006

Nick is right.

I tend to simply say, any high compression engine 9.5:1 or higher or 
any engine that is turbo/supercharged (thus increasing effective 
compression) can benefit from and sometimes NEEDS the extra octane 
rating.  You don't want knock (you'll likely not hear it anymore 
anyway due to soundproofing, etc) and knock sensors can only do so 
much.   At the end of the day, a knock sensor is responding to a 
knock already present...and you don't want any knocking (pinging) at 
all in these engines.

If you feel the need to fun 87 octane all the time in your 1.8T, 
(remind me not to buy your car) then you should be careful in heavy 
use scenarios.  Carrying various loads, up large mountain passes, 
etc.  All items that can also contribute to load on the engine, thus 
could contribute to whether knocking will happen.  Turbocharging just 
increases the chances of knocking....and thus that is why Audi 
requires high octane fuel for turbocharged vehicles.

If you feel better saving $200 a year in fuel costs, then so be 
it.  But I certainly wouldn't recommend to any high compression or 
turbo/supercharged engine owner to use low octane fuel all the 
time.  It just doesn't add up.

To the point of wasting fuel, if, because of the knock sensor 
retarding timing, you lose 10-15 hp, then during those times you'll 
need to press the gas harder to get the job done (merging, 
accelerating from stop, etc)  i.e...use more energy to do the same 
work.  That's what Rocky was saying.

At 15:50 2006-09-21, Nicholas Stock wrote:
>Can't help but give my 5 cents here...I've pretty much run 91 in both
>my Audi's with exception to a couple of 89 fillups a few times without
>noticing much difference, if any. I try and use the good stuff,
>i.e.Shell, Chevron etc...a decent detergent based fuel to keep the
>valves clean (this does make a difference). Most gas stations appear
>to only have two tanks, the 87 and the 91, the 89 coming from a mix of
>the two at the pump (hence probably contains some of the detergent
>from the high grade too - if you don't believe me see how many gallon
>counters there are on the pump you're using..only 2 for 3 different
>grades...), so 89 is probably just as good as the 91 with a little
>retardation from the ECU. If you're using a chip, then 89 seems a
>little backwards, but if it's regular driving you're probably OK. Like
>Rocky, I try and stick to what Audi says because they warranty the
>vehicle and know more about them than anybody else and to be honest,
>are you really saving that much money in the long run?
>regards to all,
>On 9/21/06, Rocky Mullin <caliban at sharon.net> wrote:
> > At 4:46 PM -0400 9/21/06, Brizax at aol.com wrote:
> > >
> > >because of the knock sensor/FI, you can "get away" with  anything.
> > >you're not saving any money this way, though, and you're wasting  fuel.
> >
> >         that's the rub right there.
> >
> >         i generally follow what audi's engineers recommend, since they
> > have a little bit more experience with cars than i do.  i feel all the
> > more comfortable doing that having toured the ingolstadt plant this year.
> >
> > --
> >   Rocky Mullin
> >
> >
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