hi,

I'm not too knowledgeable about car repair. I was trying to do the right thing for my car (1995 Legacy LS wagon) & I bought a new air filter & spark plugs at the local auto store.

 

I went in to the store with the proper spark plug numbers from the owner's manual. The guy at the counter said they didn't have that one but he cross-listed it and said the Bosch were just as good (I didn't know any different).

 

I took my car into the repair shop for a oil leak problem & I figured that since it was going to be a while until my father could help me replace the spark plugs, I might as well have them replaced while the car was in the shop.

 

When I went to pick up the car, the cashier guy told me that they replaced them, but I shouldn't buy Bosch in the future. He said the guy at the auto store was wrong and the Bosch weren't just as good for Subaru's. It seems to me that the idle knocks more than it used to (but it could be that I am just listening more closely).

 

My question is, how bad is it to use the wrong brand of spark plugs? I don't want to do any damage. Besides that, I wanted to get the best gas mileage I can since gas is expensive these days. Will using the wrong brand affect my gas mileage or performance?

 

I think I would like to buy the right ones & have the shop put them in so I don't have to think about this again. Should the repair shop do this without charge since they should have known better than putting in the Bosch? (they want to charge me for another hour's worth of labor).

 

thanks for any comments & suggestions!

The only plugs that I found to be crap are Champions (which is a shame because they used to be damn good plugs), it seems they foul quicker. I use Bosch platnium plugs with no problem. I think (someone correct me on this) that OE use NGK or Nippondenso. The wrong brand plug cant do real damage per se, just drivability issues. Even with driveability issues, that can just be a matter of finding the right heat range for your own driving needs.

 

nipper

I prefer NGK, and most people here do too.

 

Some Subaru engines work "less well" with Bosch - like my EJ20 - and others don't seem to mind - like my EJ22.

 

You're not at risk of doing any harm, but you might get a smoother and more responsive engine if you go back to NGK.

 

Don't sweat this one, though :-)

Spark plugs make sparks. If the Bosch plugs make good sparks and are the right heat range and length for the car, your car will work just fine.

 

A "Master of all Subarus" may insist on 19.99 a plug "NGK Super-Duper Iridium-platinum plugs with high-tech molecular bonding."

 

However, for normal people, ant plugs that are the right match for your engine should work fine. I have used NGK, Autolite, Champion, and Bosch, and never had any problems with any. Also, I don't fall for the "Split-fire or multiple-electrode" plugs. I am sure that doesn't make any difference, either.

 

If the plugs were not OK for your vehicle, the shop would have called you and advised you that they were incorrect, and charged you extra for the right plugs.

 

Some plugs may last longer than others, ie. platinum plugs, but any will work as long as you change them and inspect them at the proper intervals. Leave them in there until it is time to change the plugs again, and if you want to try something different, do it then.

 

Matt