The performance cars like Preludes say on the dash board to use only Premium fuel

Absolutely not - a knock sensor retards the ignition... because the lower
octane gas is less knock resistant. IOW it has more of a tendency to
detonate, when the spark occurs, rather than burn smoothly and evenly
across the combustion chamber at high compression. Therefore the spark is
retarded so that it occurs closer to TDC, e.g. instead of say 18°BTDC, it
will occur at maybe 15°BTDC.

No that's pre-ignition, i.e. spontaneous combustion as in a diesel engine.
In a gasoline engine it *can* happen in extreme conditions but is more
otfen caused by hot spots in the combustion chamber due to carbon deposits.
In a properly functioning engine with no deposits, the knock is due to
detonation when the spark actually occurs.

Rgds, George Macdonald

"Just because they're paranoid doesn't mean you're not psychotic" - Who, me??

 

On Tue, 10 Feb 2004 03:21:21 +0000 (UTC),

This is what we glean from several apparently reliable posts in
newgroups and some articles in the automotive press. Apparently Honda
has been recommending regular gas in the owner's manuals of recent
models that really could benefit from premium. It's a sales ploy.

"The Accord V-6 ratings assume regular-grade fuel, and Honda will
market it as a regular-fuel engine. But — pssst — it's good for
another 10 hp and 10-plus lbs.-ft. on premium, acknowledges V-6
engineer Asaki."

That's Honda V-6 engineer Yasuaki Asaki. See:
http://www.usatoday.com/money/autos/reviews/2002-08-01-accord_x.htm

 

yes please do add alittle....it is no always my strong suite to put
these things into words...hehe...i really only used "explosion"
because that is what everyone thinks of when they think of gasoline
igniting.(too much tv, LOL)....thanks Gordon

JT

 

Man, they let anybody in here.
Sounds like this guy knows what he's talkin' about, though.

 

They don't self-ignite _before the spark_ with too-low octane. They
get secondary flame fronts _after the spark_.

 

sure looks that way....<G>....but im not in the same "in here" as
you...LOL....rec.autos.misc. here....
JT(good to "see" ya shag)

 

Maybe, maybe not. Newer engine designs can run a lot more compression
without experiencing knocking - for example, a typical DOHC engine can run a
lot higher compression ration on 87-octane gas than a typical OHV engine
because of the better spark plug geometry, etc.

 

Actually, ignition usually occurs a few degrees before TDC.

 

Mine starts at 15 and advances from there.

 

I dunno but my Odyssey (the 3.5L V6 240HP) recommends regular but
obviously runs better and less rough on premium and it is basically
brand new (< 1500 miles). The difference is obvious, much more so than
it is on my Accord V6 (the 3.0L/200 HP version). My impression is that
most cars I have driven ran better on premium but a few did not a
difference. I can't say there was a reliable pattern. My 16-v Saturn
ran fine on 87. Some cars seem to run better on particular brands of
gas too. My Saturn got much better mileage on Mobile rather than Shell
premium (about 15% difference) whereas in my Accord it made no apparent
difference. So I think you need to experiment with this rather than
blanket statements of "regular ARCO is fine for all cars"

 

Please buy a clue before posting nonsense.