Re: 89 octane OK in 2.8L V6?

["Michael & Christine" <mlindner@netquest.com>]

:The manual says use only high octane gas (92 or higher).  I tried 89 and no
:knocking was detectable.  Am I getting less power or hurting fuel economy?  Is
:the knock sensor retarding the timing or does the car run fine on this lower
:octane?  I don't do hard acceleration normally, but even when I did I couldn't
:detect any knock or loss of power with a tank of 89 compared to perfornmace
:with 92 octane.  Comments?  Mark,  92 100S 86K

My opinion is that you'll produce slightly more power with the higher octane
stuff.  My observance of fact is that you'll get slightly better gas mileage
with the 92 octane, too.  I compared about two months' worth of driving with 89
versus two months with 92 and you'll go slightly farther on 92 per tankful than
with a lower grade.

Example:

89 Octane = $1.19/gal x 20 gal. = $23.80.  At 20.0 MPG, (400 miles) it costs you
$.0595 per mile.
92 Octane = $1.26/gal x 20 gal. = $25.20  At 20.8 MPG,  (416 miles) it costs you
$.0605 per mile.

The difference is negligible.  One-tenth of a penny per mile.

So, on a typical car you'll spend $1.40 per tankful *more* for 92 than you would
for 89.  But you'll also get an extra 10 to 15 miles out of a tank, so you're
actually not spending any more cash to go the same distance.  The bonus is a
more complete combustion and slightly more power (hard to guage, but it *does*
feel peppier around town with the 92) and, IMO, an overall healthier engine.

Of course, YMMV (pun intended)

Best Regards,

Michael Lindner
'88 Audi 5000cs Turbo Quattro
'88 VW Jetta GLi 16v
'98 Chevy Suburban