Went to Pepboys and bought a set of NGK spark plugs. Came home and put the new plugs on my 98 Civic DX. After I was done, noticed the plugs installed are for EX/HX not DX according to NGK website. FZR4F-11 bought at the Pepboys should have been FZR5F-11. Is this a major issue. The car seems to be running pretty smoothly but can't really tell because the old spark plugs were really worn out and probably were causing sluggish throttle response. I could go back to Pepboys and return the FZR4F plugs but that means more work for me. Anyone have an experience with this? I am worried this will cause long term problem even though it's running well.