Had my Spark Plugs changed this service this week ( 2014 at 56,000 miles )
It may be my imagination, but I can tell a difference I think - in a slightly smoother more responsive way.
Be interesting to see if it 'ups' the mpg at all - back to what it should be.
Though I generally get about 53-55 mpg anyway...
Well done GAS GAS now why can't Toyota have done this. Simple guide taking seconds to download and minutes to read, obviously Toyota don't follow the KISS rule.