Wish I still had the pics of the inside of my 99 200 Opti that I only ran TCW3 oil in and not DFI because it was cheaper. That engine was the reason DFI oil is the only thing that goes through the 06 model I have now. With just over 200 hours there was so much carbon build up in the motor including on the piston ring grooves that I was surprised it lasted that long. Considering the price of the DFI and how much the engine uses, it is just cheap insurance.