Hello All,
My brother will be replacing the spark plugs gasket (passenger's side) valve cover gasket (pasenger's side) and the thermostat on my IS350 this weekend. I am wondering if the drive belt will need to be replaced as preventive maintenance. Car is @ 106k miles. The belt still looks good.

I replaced the spark plugs the other day and found a little oil in the spark plugs. However, I noticed big gas mileage improvement after the spark plugs were replaced. I got average 32mpg @ 60mph. It was around 25-26mpg before the spark plugs replacement. Oh, I also added the K&N air filter. So, I am not sure if the spark plugs or the air filter that made the gas mileage improvement.

I'll be adding the F-Sport air intake on Sat as well :-) Parts are on their way

 

It's a good idea just to change it out rather then for it to fail on you. There's no recommended interval to replace it but some say 4 years just as preventive maintenance. I changed mine out at 50k just for the fun of it while I had Automotive class at school and they had the tools I needed for the job. It was almost like new still. Just know that the tensioner screw is a reverse thread. I thought I was tightening it but it didn't tightened and actually fell apart. You have to turn right to loosen and left to tighten.

 

well you change them out when you see cracks on the inside part of the belt but if you want to change then change it.