The sticker and notes in the owner's manual telling you to use premium fuel are meaningless. The price at the pump is what should determine the fuel you use, not some dumbass engineer who probably doesn't even know what gas costs these days.

Same goes for this B.S. about using some "special" coolant; you will save money by running just distilled water, just do the -10C mod so the engine fan comes on at 188F instead of the 206F it does now, you've got to keep the coolant from getting anywhere near boiling, the -10C mod will keep the engine from going over 195F, ever. (The thermostat opens at 195F.)

You can save even more by running 10W detergent oil from Walmart instead of "synthetic" oils that can cost up to $9 a quart. In fact, lower octane fuels pollute less and therefore contaminate the oil less as well - if you run 85 octane, I bet you could go 15,000 miles on an oil change - now there are some big savings.