Must I treat the owner's manual octane recommendation as gospel when filling up?

Dear Tom and Ray:

While a faithful reader of your column, I note you have excelled as marriage counselors in domestic disputes regarding cars. Here's another one for your therapy. The handbook for my wife's '94 Toyota Camry V6 specifies a minimum fuel octane rating of 91. Trouble is, this costs 15 cents per gallon more than 87 octane. She insists 91 is gospel. I am of the old school that says any octane that doesn't cause pinging is good enough. We agree to kiss and make up while abiding by your decision.

TOM: Well, kiss, make up, and fill 'er up with 91, Jim.

RAY: We always tell readers to use the exact octane recommended by the manufacturer. Using a higher octane is a waste of money. But using lower octane can cause engine damage due to pre-ignition or "pinging." Toyota has tested this engine and concluded that it has a tendency to ping if run on less than 91 octane fuel. And we believe 'em.

TOM: You may not hear it pinging, but that doesn't mean it's not happening. It may ping under hard acceleration or when you're climbing hills, times when the engine noise may mask the pinging.

RAY: You bought a $20,000 car, Jim. I wouldn't chance ruining the engine for 15 cents a gallon. Remember, it's the stingy man who spends the most.

RAY: And when that happens, remember, the stingy man's wife never lets him forget about it.
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