Bob et al:
I am on my third Audi A4 with the same 1.8 T engine that you have in your
Passat. I have always run each of them on the lowest cost (and thus, lowest
octane) gasoline available. There are few negative consequences of doing this,
none of them harmful to the engine, with the following caveats:
o If you ever take your car to a track event and want
every last bit of power available, use premium. In fact,
use it for a tank or two before the event to be sure of
having the best fuel mix on board.
o On a blisteringly hot day, pulling a trailer uphill for
an extended haul, with the A/C on Max Cool, you
might want to consider premium. At nearly any
other time you can run regular without anxiety, but...
o You will probably experience a minor decline in
fuel economy
o Maximum power under hard acceleration will be
curtailed as the knock sensor selectively dials
back ignition timing to eliminate pre-ignition and
knocking
o Power at moderate RPM with a wide-open throttle
may be lower. Imagine a passing situation where
you give it full throttle without downshifting. This is
a high load condition where the knock sensor will
dial back timing with low octane fuel whereas
premium will let it use a more aggressive advance
curve resulting in more bang
Fuels today nearly all have the necessary detergents and other ingredients
to prevent intake path deposits (previously one of the few other reasons to
consider premium gas). If you are obsessive compulsive about extracting the
last
bit of performance you might (emphasis, might) actually be able to detect
the day-to-day performance difference between the use of low octant and
premium
fuel. For most people, it's imperceptible and inconsequential.
The bottom line is that the engine is robust and, by design, can hold up to
hours of flat out running as might have been possible in Germany on the
Autobahnen, until they also got too crowded for this kind of thing. The knock
sensor is your safety net. Only under what we would consider extreme duty
conditions would premium be worthwhile. And that kind of driving is illegal in
most
states.
Bob Sharp
64-ish TR4
(and serial Audi owner)
______________________________
In a message dated 4/25/2006 5:30:51 P.M. Eastern Standard Time,
owner-triumphs@autox.team.net writes:
Date: Mon, 24 Apr 2006 13:12:55 -0400
From: "Bob Danielson" <75TR6@tr6.danielsonfamily.org>
Subject: [TR] Non LBC.....Octane Impact
Sorry for the non LBC content but I figure this list will have the answer to
my question.
I've got a 2004 VW Passat 1.8T that "requires per VW" premium gas. Last year
when Katrina pushed gas over $3.00 a gallon I tried running the car on
regular 87 octane and saw no change in performance. I know that today's cars
have anti-knock sensors that (I think) advances/retards timing to prevent
knocking at the expense of performance. Since then I've gone between premium
and regular and can see no difference. We just got back from a week of baby
sitting the grandkids and I averaged 32 mpg at 65 mph for the 700 mile round
trip, all run on regular 87 octane.
My question is: is there any long term impact from using regular gas other
then more $$$ in my pocket?
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