Hi Folks.

I'm going to replace a s5 TII with a s4 TII engine. Since the s5 needs higher octane fuel - which fuel do I need after the swap? Because I use only the s4 short block which has lower compression with the other s5 components (the ECU still needs to think its a s5 engine).

Harry

 

I always recommend "premium" in TIIs, but the manual says you can run regular old 87 octane. I would still say to run a higher octane fuel.

 

id run premium fuel allways, 1 good knock can blow a motor, so id do it to be extra safe anyway!