[s-cars] let's talk about spark plugs

[Sean Douglas]

Mike:

Short answer - why stray from the manufacturer recommended plug that is
tried and true?

This plug will last upwards of 50,000 km which is 2-3 years for the average
driver.

Assuming the other plug lasts the same time, at a $10 premium over generic
plugs, we are talking about $16-25 more per year.

Why bother?

Unless of course someone can prove that a different plug is better.

Cheers,

Sean Douglas

> -----Original Message-----
> From: s-car-list-bounces at audifans.com [mailto:s-car-list-
> bounces at audifans.com] On Behalf Of Mike Fitton
> Sent: December 28, 2006 10:24 PM
> To: S Car List
> Subject: [s-cars] let's talk about spark plugs
> 
> I'll use this as my starting point:  I'd really prefer not to pay
> $13/plug if I can help it.  That said, I will if I have to.
> 
> Okay, the stock plug is the F5DPOR.  Bosch's platinum plugs are never
> cheap.  I remember dealing with this several years ago when I had a
> Corrado G60.  That engine is extremely sensitive to plug choice.  The
> plug for that car, IIRC, was the W6DPO, also at around $13 each.
> Conveniently, Bosch also makes a W6DC, which is identical except that
> it's copper instead of platinum.  Copper conducts better, but doesn't
> last as long.  At $2 each, this wasn't a big deal.  You have to replace
> the plugs every 20k miles or so, but the PG engine is known for eating
> plugs no matter what.  W6DPOs do well to last 60k.  For a comparison,
> the guy I bought it from had installed F6DTCs, which I believe were
> appropriate for those 16v CIS I4s (RD?), shortly before I bought the
> car.  They lasted about 1k into my ownership, and I drove the GTI for a
> few weeks while I figured all this out.
> 
> Bosch doesn't, however, make an F5DCR.  Three minutes of diligent
> searching has revealed that Advance has a few NGK plugs for the AAN
> application, and I recall some NGK being the only real alternative to
> the W6Dx plugs that would last more than a month.  So my extremely
> limited opinion of NGK has since been a little higher than all the other
> retail plugs.
> 
> I think the AAN is equally sensitive to plug choice as the PG, but for
> different reasons.  I'm mostly worried about plug choice affecting the
> rest of the ignition system.  In my head, a copper plug has less
> resistance and will make the coils and stuff last longer.  On the other
> hand, sometimes the way it works in my head has nothing to do with the
> way it works in my engine.  The NGK plugs also have a 7 in the model
> number rather than a 5.  Maybe they just measure heat ranges
> differently?  I dunno.  I'm not completely fluent on all the impacts of
> adjusting the heat range, so I'm not prepared to adjust that without
> knowing exactly what I'm doing.  On the other hand, I would very much
> like to move to a copper plug because they'll definitely be cheaper and
> maybe they'll make everything else last longer.
> 
> Okay...discuss.
> 
> -Cheers!
> Mike
> 
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