I have a 84’ RX-7 and i believe the engine to be seized, it has been sitting a while and believe it to be some type of carbon lock. While searching for solutions I keep getting 2 answers, either squirting oil or ATF into the spark plug holes. I would like to know which one is better (if there’s any difference) and why? Thank You.

 

ATF will work but it also swells seals. Oil won't break up carbon. You can also use SeaFoam. It's good at removing carbon.

 

welcome to the board.

+1 on the Seafoam.