Hi All---

I've replaced probably hundreds of spark plugs in my cars and trucks over the years---In US domestic iron, and German and Japanese aluminum heads---These are the tightest I can remember removing. (It's been a while since I removed any that hadn't gotten some anti-seize)

I'm at 103,000 miles, a bit past the replacement time, but it runs like a top (now that I cleaned the throttle-body!) The engine compartment is pretty clean---some dust, but next to no greasiness. Everything under the snap-on shroud is clean---no corrosion.

I have walked up to the line in the amount of effort that I feel comfortable using to remove these plugs.

I'm considering a squirt of penetrating oil down each spark plug tube and letting it sit overnight. This Mazda is also the most modern vehicle (2010) I have ever worked on (or owned.) Do I risk some reaction or contamination that would mess with the computer's sensors or some other thing?

Many Thanks!

JW