Sparkplugs
 

2013 Toyota Corolla , has 63117 miles on it. It's been getting crappy mpg lately.
Started to get a misfire randomly code p0300. Changed plugs and coils.
Ceramic is burnt. Trying to attach picture for you guys to see. Electrodes are gray.

Found this on line.

What Causes a P0300 Code?
Low Fuel Pressure
Vacuum Leak
EGR system malfunction
Internal Engine Problems (such as low compression)

Less Common Causes
Faulty Coil
Faulty Spark Plugs and/or Wires
Camshaft or Crankshaft sensors
Ignition module
Computer