I've got a 98 LX470 with 197K miles on it that I got handed down from my parents. Unfortuntely, they dont keep service records and have no idea when the last time they changed the plugs were. When I pulled them, they look new, but I was wondering if anyone knew of a way to see if spark plugs were worn out. Like I said, cosmetically, tjey look great.

I've driven a new LX recently, and it definitely had more torque off the line. Im thinking that its possible the spark plugs need changing, but they seem to look OK. If the iridiums were like $3, I would just replace them and be done with it, unfortunately, they cost like 4 times as much and Im hesitant to replace them if they dont need it.

Anyone have any suggestions?

 

Look at the head of the spark plug... that small peice of "hook" looking part, and how worn out it is. This should be a good indication of how old they are.

 

Agreed & also look at the 'electrode' as well.......I understand your concern with Iridium spark plugs......however remember they are good for 120,000 miles untill they need replacing so in the long run, they probably save you money (especially on labour say one major tune up vs. 3 - 4). What kind of plugs are they anyways? NGK or Denso?

 

the ones that are in there now are the Denso SK20R11. I guess I'll have to pull a plug again to look at the hook. The things are so small though, its hard to tell. They are clean, so thats why Im thinking they must be relatively new.

There's no pinging when acclerating, but its just so slow compared to the newer one I drove. Unless thats what happens after almost 200K miles.

 

I used Bosch Platinums in my LC, and it's been fine for 20k now. I plan to change them every 60k.

Performance wise, I saw no difference at all. So base your decision (iridium vs platinum) on whether you want to save money on the plugs themselves, or whether you want to save time (60k vs 120k replacement interval).

I like wrenching around with cars, so I chose platinum.