i picked up ngk Iridium plugs for 2003 volvo s40. they say not to gap but its at 33 and book calls for 28 on double platinuims.
can i use them as is or take them back? Do iridium help gas mileage, @$4.30 a gal. it would be worth it
to raise mileage.
always gap, will not save on milage -especially if you do not gap, but overall power, pickup and starting will be improved so yes you will save gas. Nice plugs
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