I personally wouldn't take the chance. The ~$0.20/gallon savings is insignificant even over long periods (for instance, it'll take you more than 25 fill ups to save $100 by going with cheap gas).

Dropping the octane increases the likelihood of knocking, even with sophisticated knock sensors. One good rattle and you're replacing head gaskets (although on a non-boosted car, this is less probable). These are relatively high-compression engines, so pulling out spark may not cure knock under all conditions, either.

I'll also wager that mileage will go down, since the car will not be running at peak efficiency any longer, and with less power, you'll need more throttle to make it perform normally. At best, it may be a 0 gain.

For four bucks, I'd skip it.

_________________
Matt in Cleveland
My 1941 Buick Century restoration



Mine:
2004 allroad 2.7T Tip
Burgudy Pearl/Platinum+Saber Leather
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