My car is driven 70k km which is about 35k miles. The plugs have never been changed. Should i change them?

 

If you have a pulley or jcw car, every service...so about every 30,000 miles..
A standard S is scheduled for 90,000 miles I think....might be a bit high for a SC'd motor...not sure on a Cooper.
Always do them on a cold head, and use a tourque wrench... Then to be safe, check them in a few weeks for tightness!!

 

how much torq should I apply to them?

 

20 LBS. COLD. I only replace Mini plugs after an overnight without starting. Never had a problem with stripped threads.

///Rich

 

stripped threads?

 

Too tight, the soft alloy gets stripped, too loose, the plug gets pushed out, ripping out most of the threads...
It can sometimes be dealt with without removing the head by cutting new threads in place or using a threaded insert, but both are risky...both relilability wise, and the metal that falls in the motor...

 

Should also recheck every 5,000 as part of normal maint.

 

If you pull plugs out of a hot engine there is a good chance the threads will come out with the plugs. Steel plugs in an aluminium head = different rates of expansion.

If you remove, install them cold & use a torque wrench you should not have any issues. Checking them for tightness at every oil change is not a bad idea. Some folks have had plugs come loose & cause all sorts of fun.

 

Should some form of anti-seize be used and if so, what>

 

Some folks use it & some don't. I use it, but just put a very light kiss of the stuff on a part of the plug treads. As you tighten the plug it will distribute the anti-seize around the plug threads. I have a stick of Permatex anti-seize that I use. I don't think it matters what brand you use. Remember a little is enough.

 

I use the little $.99 tube of anti-seize you get at autozone or walmart