The iridium tipped OEM spark plugs of a 10th generation (2009, 2010,
2011, 2012, 2013) Toyota Corolla can last up to 120,000 miles according
to Toyota. But they should be checked well before that time if just to
make sure they are not frozen in the engine block and to inspect them to
detect any engine problems. To view my DIY tutorial to the procedure,
click on the link below.
Here's the instructions page -
http://www.paulstravelpictures.com/2009-2013-Toyota-Corolla-2ZR-FE-Engine-Spark-Plugs-Replacement-Guide/index.htmlI hope someone finds it to be useful.
Cheers,
Paul