Winter idling?

I think regular spark plugs need to be changed every 30k miles.

I had crappy Champion plugs in my new '00 Impreza and replaced them at approximately 26k miles with NGK Iridium plugs. Wow, what a difference! Much, much, smoother running engine, and they are supposed to last 60k or more.

You may check your oil if its not a bit too thick grade for winter conditions. If so, adding a small amount of Marvel Mystery Oil, just a few onces into the oil will thin it out and very likely affect/reduce the idle, a bit.

M.J.

Forgot to add that the idle went down a little, or so it seemed, I was not really paying much attention to idle rpms per se, but I think they went down.

More precisely cold-start idle rpms.

M.J.

How much more expensive are the Iridiums compared to regular?

It turned out that the problem could be fixed by resetting the ECU. However, it's true that I haven't changed the sparks in a very long time. I've changed the air filters, the oil, the fuel filters, etc., many times, but the sparks get ignored.

Yousuf Khan

They are several times more expensive. I forget how much I paid for mine, USD $9.99 a piece, or so. Taking into account that it is a somewhat unpleasant job to change plugs in a Subaru flat-four engine, I consider it money well spent, as I won't have to do it again for a very long time. The smoother running engine is an extra bonus. They claim the Iridiums also save fuel but I haven't been able to notice much difference.

I highly recommend the NGK brand.

Good to know.

M.J.

several times more expensive. I forget how much I paid for mine,

Yeah, so I went down to a couple of Canadian Tire stores yesterday to check out the spark plugs. One of the stores was completely sold out of Iridiums, and the other store had them, but the particular model that is relevant to my model had only one pair available. The price was $19.99 for a package of two. Plus some kind of a 3 year guarantee? What's that guarantee about?

Also noticed that the Iridiums were of similar shape and design to the bunch of cheaper Platinum tipped plugs. Basically they all seem to have that extra narrow point on them. I assume the only difference is that the Iridiums last longer than the platinums?

Also I don't have a torque wrench, is it advisable to put a spark plug on without a precise torque wrench? The owner's manual says I should let the dealership change the plugs on this engine.

Yousuf Khan

Supposedly they are better, not necessarily last longer than platinums.

I think they may, at least partially, pay for themselves in fuel savings. This is difficult to observe on a single tank of gas, but over 30k, or 50k miles there may be a good number of gallons of fuel saved.

Here's NGK site where the describe them and also have a nice tech section giving some very general instalation tips and other info.

Changing spark plugs on a Subaru can be tricky. If you are not very patient, or somewhat mechanically inclined, you may well let the dealer install them just like the owners manual suggests.

This is beacause the access is not very good, and primarily because there is a visibility problem. The plugs sit so deep in engine block you barely see them. This can be a bit intimidating. If you get aggravated easily let the dealer do it. Don't get me wrong it can be a do-it-yourself job, just if you are patient, don't panick, and are at least minimally mechanically inclined. Do a google search of this newsgroup, there was a guy describing here how he uses plastic tubing as an extention when positioning plugs into the deeply recessed plug holes.

I don't use a torque wrench, and I never had a problem. Remember to use anti-seize compound and do not tighten them "too much." With anti-seize compound on they tend to slip in very nicely and overtightening is a risk.

M.J.