Yes, I do know what I am doing in general, I am 43, and have been working on cars since 16, as I stated, I was unsure, being a Saturday CAstrol was not open and I didnt want to waste hours searching auto places for the Sport, thats why I rang a respected person from these forums, he advised it would be OK. I am going to ring Castrol to check, I know it's probably not the best thing to do, but seeing as I already half filled the car, maybe 3L of Sport, will the 1to 1.5 of Titanium really kill the car? Should I sue Supercheap for the cashier telling me its OK to mix and the Titanium supercedes the Sport? Maybe if I bring this up with Castrol they might give me another 5 L for free?