Check Engine Light!
 

I just bought a used 95 Protege ES and they had it inspected prior to finalizing the purchase of the car. I just picked up my car twice from the inspection station for emmisions they sent it at. 1st time, they said it was the plugs so I switched them. The new plugs happened to make my car slower. So I switched them back to the old ones. The check engine light went off. So the 2nd time I went there hoping that it is going to pass it did not. THe light came on again and said it is something else.? The 3rd time, they shut off the light and passed it. Next few days later, the light came on again! Now it is on until now...

Does anyone know what I can do to solve this problem? And what is a good oil to use for it? I just put in what it recommends for the weather here and I put Mobil 1 10W-30 w/ 1 quart of Lucas. It seems it has to crank pretty long in the cold mornings until it starts... If someone can shed some light on this, it would be greatly appreciated!:)

Did they tell you what code was in the system?

What kind of sprak plug did you put in, and did you gap them, before you put them in?

As for the oil, it doesn't matter as long as you run 10w30. I use Mobil1 all the time, and never have a problem. With the emission though, you might have oil leaking inside the comustion area (bad pistons), and this could be why your emission don't pass. That, plus wrong spark plugs could really do the trick on you.