All right, back to car stuff, but a different car: while pressing down the accelerator going uphill, I heard a little tapping in the PT's engine compartment. I've been trying to cheap out using 87 octane even though it's turbocharged. (The manual didn't say I couldn't!) So the last time I filled up I used mid-octane fuel and the tapping is gone. Which is better: filling up with higher-octane fuel, or buying an octane booster and dumping it in the tank when I fill up?

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