subsince77 Posted March 17, 2008 Share Posted March 17, 2008 This came up as part of another discussion, but I thought I would post it here. In the old days, I always checked and re-gapped my plugs. They always seemed to need it. In the last several years, I have been using better quality plugs in general, and the NGK Laser Platinums for the Subaru in particular. These plugs come gapped at .044. My Haynes manual says that this plug should be gapped at .039 to .043 for this car (97 OBW 2.5). The box says not to re-gap them because you might damage the center diode. I have checked a bunch of them, and they were all indeed gapped at .044, so at least they are consistent. I have taken to just putting them in as they come out of the box. Given the design of this plug, I don't think the gap widens much, or at all, with use - am I wrong? So, should I be re-gapping these plugs? If so, to what gap? And is there any chance that running them at .044 is causing any of my misfire issues discussed elsewhere? Link to comment Share on other sites More sharing options...
idosubaru Posted March 17, 2008 Share Posted March 17, 2008 44 is not causing a misfire. or more correctly if it is - then something else is wrong. i'd gap them to the proper specifications, taking care not to damage anything. owners manual should tell you and if those 39-43 numbers are what it says then use those. you're not going to notice a difference though except that maybe you'll need to replace them 5,000 miles sooner, but who's counting and maxing out their plugs? Link to comment Share on other sites More sharing options...
2X2KOB Posted March 17, 2008 Share Posted March 17, 2008 Do the laser platinums last a lot longer than the standard plugs? Is the extra cost worth it? Link to comment Share on other sites More sharing options...
aircraft engineer Posted March 17, 2008 Share Posted March 17, 2008 I can't say about automotive plugs - but in aircraft, the fine wire electrodes last about 3X as long as "massive electrodes" Automotive plugs are a bit different in the design, though - the center electrode is the platinum in the auto - the "outers" (grounding to the plug threaded part) are the "fine wires". I'm pretty sure the platinum in auto plugs is "alloy", probably with a copper main electrodemost of the way down the plug - but I'm not sure) I understand that the polarity of the spark changes with the "direction" (normal firing over time tends to wear the center electrode more in auto plugs) and the platinum is MUCH more resistant to metal loss thru arcing over time than "steel" so I would expect them to go 3x or so longer (YMMV, of course). Are they "worth" the premium? Your call. I'm thinking about going out into the old scrap bin I have of old plugs (I used to make metal sculptures with them) and finding the platinums and picking off the electrodes. Platinum is over $2000/ounce right now and I think I might have 2 grams of them. (that's $150 for "junk" that takes up a wire about .5mm dia. and maybe 6 inches long) <you probably didn't want the technicals> Link to comment Share on other sites More sharing options...
2X2KOB Posted March 17, 2008 Share Posted March 17, 2008 <you probably didn't want the technicals> Of course I did. Thanks. Link to comment Share on other sites More sharing options...
subsince77 Posted March 17, 2008 Author Share Posted March 17, 2008 Do the laser platinums last a lot longer than the standard plugs? Is the extra cost worth it? This engine is notoriously sensitive to plugs and wires. Lots and lots and lots of posts where people have had problems when not using the specified plugs and OEM wires. Actually, I'm now using NGK wires instead of Subaru. Anyway, that's what makes them "worth it," to me, along with the fact that they really do last forever. AE - love the technicals. Link to comment Share on other sites More sharing options...
nipper Posted March 17, 2008 Share Posted March 17, 2008 Newer plugs, depending upon what they are made of, should nOT be gapped (but you can check them if it makes you feel better). They come from the factory pre-gapped. You trying to gap them may actually brake the plug electrode. nipper Link to comment Share on other sites More sharing options...
subsince77 Posted March 17, 2008 Author Share Posted March 17, 2008 Newer plugs, depending upon what they are made of, should nOT be gapped (but you can check them if it makes you feel better). They come from the factory pre-gapped. You trying to gap them may actually brake the plug electrode. nipper That's what I thought, just running down every possibility on the mis-fire front. Thanks. Link to comment Share on other sites More sharing options...
2X2KOB Posted March 17, 2008 Share Posted March 17, 2008 This engine is notoriously sensitive to plugs and wires. Lots and lots and lots of posts where people have had problems when not using the specified plugs and OEM wires. Actually, I'm now using NGK wires instead of Subaru. Anyway, that's what makes them "worth it," to me, along with the fact that they really do last forever. Hmm.. But plats aren't what is specified, standard NGK BKR6E-11 plugs are. I guess the fact that you won't have to change the plats for 100k miles helps a lot. I'm also using the NGK wires, they seem to be doing all right so far. I only got them because I couldn't get that goofy Trademotion parts search app to find a set of OEM wires online. Link to comment Share on other sites More sharing options...
subsince77 Posted March 18, 2008 Author Share Posted March 18, 2008 Hmm.. But plats aren't what is specified, standard NGK BKR6E-11 plugs are. Both my owners manual and Haynes say PFR5B-11. This is a 2.5. I'll say it before someone else does, yet another side benefit of the ej25 - expensive pugs that are hard to install. Link to comment Share on other sites More sharing options...
2X2KOB Posted March 18, 2008 Share Posted March 18, 2008 Both my owners manual and Haynes say PFR5B-11. This is a 2.5. I'll say it before someone else does, yet another side benefit of the ej25 - expensive pugs that are hard to install. I'm working on a 2000 OBW 2.5 4EAT, just verified that the BKR6E-11 plugs are specified in the owner's manual and the FSM. I guess the PFR5B-11 are the platinums? What are you driving? Actually changing them wasn't too difficult but this is a single overhead cam. Mostly I worry about the threads in the head. The plug gap range is 0.039" - 0.043". The new BKR6E-11 plugs checked fine at 0.040" right out of the box. Have no idea how many miles are on the old ones (59,000 that I know of) but they were visually in good shape colorwise but the gap had worn to about 0.070" to 0.090". Link to comment Share on other sites More sharing options...
subsince77 Posted March 18, 2008 Author Share Posted March 18, 2008 What are you driving? Actually changing them wasn't too difficult but this is a single overhead cam. Mostly I worry about the threads in the head. 97 OBW 2.5L DOHC. Link to comment Share on other sites More sharing options...
mdjdc Posted March 18, 2008 Share Posted March 18, 2008 I went to the dealership and the plugs recommended for the 2.5 DOHC is the NGK iridium plugs. I'm not sure of the part #. At the stealership they run 12.00 each, but with the degree of difficulty in installation it was worth the expenditure. I had to jack the engine up on each side so I could gain easier access for removal and installation. A simple job made difficult by design. Took about 45 minutes to change the plugs and wires. Did help my gas mileage thoughso, maybe it will pay for itself over time. Link to comment Share on other sites More sharing options...
calazo Posted March 18, 2008 Share Posted March 18, 2008 I have always regapped the plugs on all the cars I have ever owned with good results. I have never broken an electrode in the process. I'm not sure if it is 0.040, but in the metric system I usually gap them at 1.1mm, as long as that the ignition is electronic and thus provides a strong spark. The NGK spark plugs usually come out of the box with a narrow gap (narrower than usually recommended, I think). After gapping, I have never had a misfire, except when I used to try those fancy Bosch 4-electrode spark plugs which only work for German cars, of course. For Subies, NGKs are best (Nippondenso are also recommended, but I think they are harder to find...). I currently use NGK's BKR5E or BKR5E-11 (indicated for cold weather, high altitude, good running engine) in my EJ-22 engine. Link to comment Share on other sites More sharing options...
OB99W Posted March 18, 2008 Share Posted March 18, 2008 The NGK plug numbering system can be found at: http://www.ngk.com/sparkplug411_ngk.asp The "-11" indicates a 1.1mm (.044") factory gap, but others can be had (although perhaps only by special order). Link to comment Share on other sites More sharing options...
2X2KOB Posted March 18, 2008 Share Posted March 18, 2008 I had to jack the engine up on each side so I could gain easier access for removal and installation. A simple job made difficult by design. Took about 45 minutes to change the plugs and wires. Jacked the engine and it still took you only 45 minutes? You should go into business. That would take me four hours. Link to comment Share on other sites More sharing options...
subsince77 Posted March 18, 2008 Author Share Posted March 18, 2008 It usually takes me about 45 minutes to an hour to do plugs and wires in that car. For the left side I remove the battery, then unbolt the washer fluid tank and lay it where the battery was. That provides plenty of clearance. On the other side I pull out the whole air filter box. Sometimes I remove the bottom portion of it, sometimes just the filter and snorkel part. That gives plenty of room on that side. Gee, aren't you supposed to have to dismantle the engine compartment to change your plugs? I've gotten used to it, and I still love the car. You don't have to do this very often if you run good plugs and are not having the STINKING mis-fire problem that I have been having. I used to go years between plug work. Link to comment Share on other sites More sharing options...
shortlid Posted May 19, 2008 Share Posted May 19, 2008 Well just put a set of NGK lazer plats. in my Mom's '03 GT auto. with 63k. Well the diff. was huge over teh Regular NGK that I replaced at 30k. Best MPG ever out of the car as well. I will put nothing but Plat's in it now!! Link to comment Share on other sites More sharing options...
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