OM Plugs - Iridium Plugs. Advantages

[TonySR]

What are the advantages of using Iridium plugs on a standard engine? Will it make a difference like this bay ad claims?

http://cgi.ebay.co.uk/vauxhall-ASTRA...mZ250077606563

[Tahrey]

Hmmm, well they have a cool sounding name at least
For the starting and long life claims, well, I can't say I've ever had a problem on any car i've driven with bogstandard cheap ass plugs that could have come with a halfords own-brand on the box. Astra for one will typically fire in a couple of cranks and hasn't ever gone wrong thanks to sparks (only the HT leads).

As for the improved power claims etc... I doubt the 0.7 second reduction really - and what engine/car is that, by the way? It doesn't say... I could believe it for an 80s-vintage 1.05 5-door Golf with all the option boxes ticked, which had an official 0-60 of something like 22 seconds, as even a couple of percent improvement (say 45 to 46hp) could make a small but measurable improvement. Might not do much for making yer 7.6-second-to-60 turbo weapon a sub-7-seconder...
It might cause some improvement though through better combustion IF it's not a load of marketing bumpf... thanks to most cars now having oxygen/lambda sensors. Standard payload of fuel is delivered at WOT, slightly better spark (in whatever way it's actually "better", i'm not exactly an autoelectrical engineer) means it burns more than expected, lambda value is pushed a bit more towards "this mix is too lean", sensor reports this, ECU sticks a bit more fuel in with the next squirt, this burns completely = more power, and the lambda ratio stays at "just right" so no further alteration. Note that it didn't state "better fuel economy" on the write-up

How much are they though? £25... that'd probably be worth a gamble just so as you can find out for sure - get a set, nip down your local rolling road merchant and do a run on each set (or to be scientific, 3 for each, to weed out any freak results) and see if they improve your power and/or torque.