Penzoil XLF and synthetic blend is just fine for carb and EFI twostrokes. On the Optimax, you need to use the Merc/Quicksilver DFI. The Merc/Quicksilver Premium Plus/Synthetic Blend is an acceptable substitute and can be mixed with DFI. Merc and Quicksilver are the same oil and both made by Mercury. The QS was made to sell to non Mercury dealers like Walmart. The DFI and Premium Plus have s specific flow rate to propperly lubricate the compressor on the Optis. I once had a customer using Walmart Supertec oil in his Merc 250ProXS. He found out the hard way that compressors are around $1,000 before tax and labor.