i had a d15b7 in my del sol before i swapped it out. i know if your like me you try to get every lil uumph out of it but that can kill it very quick.Is there any smoke coming out of the exhaust if so what color? what kind of miles do you have on it? there maybe alot of carbon built up on the pistons too. that would dirty the spark plugs. did you do a compression check if you did what number did you come up with? bad rings will cause you to burn oil and in my mind its an easy fix but not worth it. i would do a compression check. where are you located cuz i still have my d15b7w/ tranny with 94k miles on. i just need to dig it out of my brothers garage. if your lookin for a little more power and a pretty easy fix i would just say swap in a d16. i picked up my d16 with a tranny up for $150. running condition