The heat range of the plug has nothing to do with the fuel mixture or the
overall temperature the engine runs at. The heat range rating is a measure of
how fast the tip of the plug cools off after ignition. If it cools to fast then
you get crap build up on the tip and fouling, resulting in miss fires. If the
plug does not cool down quick enough then it can/does cause detonation (i.e.,
pinging).
You can visually see the difference in construction between a hot plug and a
cold plug. The ceramic insulator on the center electrode will go further down
into the body of the plug before making contact with the metal housing of the
plug on a hot plug compared to a cold plug. This results in it taking longer
for the heat build up in the tip to disapate into the head of the engine.
The only reason to put a 3923 plug into your engine is if you have been having
detonation problems. Getting reduced fuel mileage would be an indication that
the plug may be fouling resulting in a slight miss fire. I would go back to a
stock heat range.
Dave Clement
99 SLT+ CC 4x4
In article <BAY11-DAV128UR6xW290003ef3c@hotmail.com>, hemidak@msn.com ("Chad
Evans") writes:
>
>
> 3923's are one range colder. colder = more fuel ? better for performance.
>
>
> ----- Original Message -----
> From: "Jay & Dana" <jay&dana@telus.net>
> To: "DML" <dakota-truck@dakota-truck.net>
> Sent: Friday, February 20, 2004 6:49 PM
> Subject: DML: Autolites & gas mileage
>
>
> >
> > I know the majority here on the DML use the Autolite 3923's but I'm
> > wondering if anyone has experienced an increase or decrease in fuel
> > mileage
> > since switching over to these plugs from the stock ones? On my 97, 318 it
> > seems the gas mileage has gone down slightly since using these plugs.
> >
> > Jay
> >
> >
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