You could fill half with 91 and half with 87 if it's really important to you. I presume Costco does this because most people choose either 87 or 91, so they save on having to have a third storage tank installed, gas truck delivery, etc.
Mid grade fuel is mixed at the pump...most places
Yeah, from what I've experienced they only offer low grade and premium. There's no point in fueling with midgrade fuel. If you want to enhance the performance of your engine and have your vehicle go longer between maintenance intervals, always fuel up with premium- 91. It really does make a difference in the long term aspect of vehicle ownership/maintenance. Less wear on your fuel injection system, less gunk and build up on your valves/ pistons and gaskets. California has different petroleum regulations and ethanal standards, so the standard for our state is significantly lower than anywhere else. ... Just trust me. Always utilize 91.
Thanks @Tiffany & @Michael ... It makes sense now. I appreciate the info. 🙏
Costco only has the 2 grades 87 and 91 that's how it's been since they've opened and started selling gas.
Not sure why, but all Costco's only sell 87 and 91 octane.
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