It’s about time for major maintainence on my 1995 Subaru Impreza and along with the filters, belts, and so on are the spark plugs. Looking at Wal-Mart I have three options. The cheap copper ones at about $3 a pair, the platinum ones at about $5 a pair, or the gapless platinum ones at about $9 a pair. So, two questions. First, are the platinum spark plugs worth the extra money? And second, is there any advantage in the gapless plugs as compared to just gapping them myself?
Most standard plugs will work, but I would go with the same brand and part number that Subaru originally used for your car. I can’t find it on Google, but the dealer may be willing to tell you. Being a Japanese car, I’d guess that it was originally fit with Nippondenso plugs, possibly NGK.
Most cars do fine with standard spark plugs from any of the major manufacturers, but there may be exceptions. For example, I used to work on Japanese motorcycles, and swore off ever using Champion plugs after “repairing” poor-running bikes by pulling the Champions that the owner had put in and replacing them with Nippondenso or NGK plugs. Then, I bought a Jeep Cherokee and was told that the engine would run better with Champion plugs than with any other brand.
I’ve tried platinum plugs with the thin electrode in other cars and found that the car didn’t run as well as it did with the cheaper standard plugs.
I wouldn’t use the gapless plugs unless Subaru used them in the first place. I’m not sure which brand Wal-Mart stocks, but Splitfire came under fire years ago for claiming that their plugs improved mileage and performance. Independent testing didn’t back them up.
As a recent victim of spark plug failure, I would suggest using factory-specified parts. If you don’t, your mechanic has a ready-made excuse for ANY problems down the line.
I fix cars for a living. Whenever possible (which is almost always), I use the brand and type that was put in at the factory, or the factory-recommended alternative (e.g. NGK or Nippondenso for many Japanese vehicles). For your car, my sources show it to be NGK 2756 (= NGK BKR6E11). If you can’t get these particular plugs at Wal-Mart, I think it’s worth the effort to go to an auto parts store that carries them.
While different brands from the original may be suitable and work okay, there are cases where they will cause problems. It’s usually just as easy to stick with the original. They may cost a bit more (sometimes they don’t), but going with a cheaper brand is often a false economy.
In general, if the car came with platinum plugs, absolutely use platinums. If it did not come with platinums, it usually won’t hurt to use them but I question that there’s much point to doing so. Fancy designs that are highly touted by their advertising copy as “upgrades” almost never live up to the hype.
Thanks for the help. I tried the NASIOC forums and got a lot of back and forth and different opinions and talk about things I’ve never heard of, like how hot the spark plug is. I’ve just got the standard 1.8 L engine and have a hard time believing that it makes much of a difference whether the plugs are made of copper or platinum or iridium or any other element, other than what the car originally came with. I take the cynical view that 90+% of “performance mods” are complete crap. That’s why I asked here.
It is my understanding that platinum plugs wear longer rather than improving performance. Whether they wear long enough to justify the price is debatable. However, they are definitely worth it if you don’t check and replace plugs as often and recommended. Using standard plugs is great advice, almost as good as maintaining the service interval.
Can someone comment on this? I have also heard the bit about platinum wearing longer than “regular(copper?)” but at the cost of some power. True? How and how much are we talking about? The ancient MR2 I bought this summer has Bosch platinum 2 electrode plugs. Very pretty I have to admit, but would these be ill-suited for a small Japanese sportscar to the point where I could screw some NGKs in there and feel a difference immediately? The car is old enough that I’m already inclined to do very frequent maintance on it just to arrest any further aging–the thought of replacing spark plugs twice as often doesn’t really bug me.
Inigo, I suspect that a lot of info about performance differences between different spark plug designs will be anecdotal. Platinum electrodes are used for durability. I question whether they somehow offer less power. The issue hasn’t really been raised in the auto repair field, where experience has shown that sometimes deviating from the car maker’s recommendation can lead to problems. Our priority is avoiding those problems, not experimenting to find minor performance enhancements.
I Googled on “spark plugs” design platinum compared and found these two sites that seem to have good general information:
http://www.aa1car.com/library/2002/ic120214.htm
Most of the other sites are associated with manufacturers or retailers.
My philosophy is that we don’t know ALL the reasons why automotive engineers choose one type of plug over another for a particular engine, and it’s taking a chance to second-guess them and use something else based on limited knowledge.
If your car is not modified, you do not need to worry about changing spark plugs to a colder heat range. Do as Gary T says and get yourself to either a Subie dealer or a NAPA and pick up four NGKs. Your car will thank you.
Inigo, for a Toyota, I definitely recommend factory plugs. They may make the car run smoother, and get you better mileage than the Bosch plugs. Actually, for any electrical part on a Toyo, I always buy factory parts.
[Slight hijack]
I have a VW Jetta with a 6 cylander engine and a 5 speed stick. An acquaintance, who may or may not know what he is talking about, has told me that I would get better performance by replacing the plugs with ‘double-tap’ plugs. He seemed to imply that they (‘double-tap plugs’) fired twice as frequently as regular plugs and would thus boost the car’s performance throughout the power range of the engine.
Reading the links above, I’m starting to think there is no such thing as what he described. Can someone please verify his brilliance/idiocy for me?
Also, aside from selling it, are there any suggestions for power/performance improvements for a VW Jetta with the specs listed above?
(and no, it is not JATO-compatable)
Thanks!
WTF?
A spark plug fires when the distributor tells it to fire. The purpose of firing a spark plug is to ignite the air and gas mixture after the compression stroke. They only need to fire once per cycle. It’s not like you are going to magically acquire more cycles, so what are you going to do with the extra spark?
The only think I can possibly think of that these “doubletap” plugs would do would be to fire twice in very quick succession, maybe lighting off any unburned fuel that was left after the initial ignition. Dunno what effect that would have on your power, driveability, or longevity, but if I had to guess, it would be bad.
I seem to recall someone doing something like that to a rotary engine with beneficial results, though. I will have to look for a cite…
:smack:
Duh, that’s what the trailing plug does on a rotary engine. n/m 
Idiocy. Necros is right, the spark energy originates in the coil, and the plug can only convey what is sent to it by the coil. If you want the plug to fire more often, the components that trigger the coil (in the distributor on older cars, typically in the computer on newer ones) have to be designed to accomplish that.
I’m late to the party, but can I play too?
I used to have an uncle that owned his own shop. He stocked three different brands of plugs. Autolites for Fords, ACs for GM and Champion for Chrysler. You could not get him to use any brand of plug except OE. Of course this was 30-50 years ago.
Fast forward to today.
I will guarantee you that if you put a Bosch, AC, or NGK plug in a modern Volvo, you will get a mis-fire and a check engine light. This problem is so common that when a customer comes in and says that they had a tune up else where and the car runs poorly, or has a check engine light, the very first thing a tech does is pull a plug to see if it factory or not. If the plug does not say Volvo on it, they install factory plugs. this seems to fix about 9 out of 10 of this type of running problem.
As far as platinum plugs (Bosch) goes, back in the day, I ran Bosch Platinum plugs in my performance cars. They worked great in MGs, Triumphs, Austin Healeys, and early 911s. Again fast forward to today. I have not heard anyone tell me that Bosch platinum plugs worked OK in their car. All I ever hear they had to take them out and put regular plugs in instead.
I am firmly in the use the factory plug category.
Count was he maybe talking about multiple electrode plugs? They only fire once, but they are more misfire resistant, and as a result are less likely to trip a check engine light on an OBDII car.