Is Nissan's 105K mile spark plug cycle too long?

[Chuck Tribolet]

Is Nissan's 105K mile spark plug cycle too long?

I have an '01 PF, and the gas mileage has dropped by about 3 MPG the lastmonth or so. It had been 83K miles since I changed the plugs last, so I figured I'd try a new set of plugs, and changed them out on Saturday morning(almost three hours and a knuckle-buster). The jury is still out on the gasmileage, but it did seem better Sunday on my usual 100 mile round-trip towing my boat. The truck definitely pulls high RPMs and hills better. The Prunedalehilll was just doable in fourth gear (I have a stick) and is now comfortablein fourth, the Carmel Hill had needed third gear and is no just doable in fourth.

The plugs that came out were a text-book tan color (perfect mixture, but that'sexpected today) but the gap had opened about 50% (by eyeball comparisonwiht the new plugs.

What's everybody else's experience with plug life on the 3.5L?

[Densetsu]

I bought my Pathy at the 70k mile mark and replaced almost all the maintenance items at the 78k - 80k mile mark. I did this in stages to see how the maintenance items affected fuel economy... there was a 1 - 2% increase with all the fluids, filters, etc, and a 10% increase when the plugs were changed.

Like you said, plugs looked normal for that amount of usage, though I didn't pay attention to the gap on the old ones.

I assume that shortly after the 105k mark the chances of significant power loss, poor fuel economy, or outright spark plug failure increases significantly, and that's why Nissan chose that number. But there's no problem with changing them early, say every 70k miles.

[Pwnin O'Brien]

I would say if you do mostly city driving then I would change them around every 50,000 miles.

[Chuck Tribolet]

I don't do a lot of city driving. It's mostly freeway and country roads. Butdo about 200 miles with my boat trailer every week.