Okay I'm new to the who DIY scene and working on my TL so this might comes off as a dumb question. I had a garage mechanic down the street change my spark plugs on my 02 TLS. I replaced the original spark plugs with some NGK Iridium IX. I noticed he didn't gap them before he put them in and when I asked him he said they were already gapped where they needed to be. Is this true? I'm a bit doubtful about that statement but I wanted to get other more experienced TL owners opinion. Also when should the oxygen sensor be changed and where exactly is it located?

 

The plugs come pregapped and have a special super fine wire electrode- you cant use a normal plug gapper on them anyway
Part of the numbering system of plugs includes the gap setting, heat range etc

The O2 sensors- one in front and behind the cat, will tell you when they fail with a check engine light- or poor gas mileage suddenly.
Its not a routine maintenance replacement item so dont sweat them.

Do a seafaom cleaning of the gas and intake manifold and make your TL run like new!