Once my Dad was just FLOORED I am paying for premium. He talked about mixing regular with premium, driving nicely with regular, and using octane boost to save a few pennies. Using today's gas prices and the price of not using premium at all here is how the numbers run for me.
Regular $3.85(9), Premium $4.15(9) at the local Chevron (always about the 9).
18 gallon fill-up.
Regular fill up @ 3.859=$69.462 (btw 3.850=$69.30
that 9 is a killer )
Premium fill up @ 4.159=$74.862
Bottle of 104+ octane booster: $8.99+tax
Cost of a blown head gasket trying to get around a slow person up a steep hill in hot weather with $5-$8.99 in my pocket; with the switch in premium and boost turned back up "just a pound or two" because I got tired of how much of a dog it was and I trusted I'd remember to go easy on it.
The $5 a tank is head gasket insurance to me.
A round trip ticket to the same place (Sacramento) is now about the same price as the 4 tanks of gas I use in a round trip drive.