As some may know, I have an MR2 turbo and I run it on Shell Optimax, as recommended. It is my understanding that the use of normal unleaded will not cause damage to the engine but you simply lose performance with the lower ron value. Is there any equivalent to Optimax made by Esso or BP ? Also, I have heard that by adding a small quantity of kerosene to normal unleaded that can increase the ron value to enhance performance. Is there any truth in this ? Cheeaaz.