If you don't have the owners manual, take the plug to Ace Hardware and match it up with a metric female nut for sizing.
Porgy Tirebiter: "Heavy on the 30 weight, Mom."
2017 Toyota Camry XLE, 12K, 2nd owner
2007 Honda Ridgeline RTS, 97K, original owner
2007 Infiniti M35, 115K, original owner