Volvo: Spark Plugs and fuel, motor octane number, research octane number

Question
QUESTION: I am replacing the spark plugs in my 2000 S70 non turbo and looking for a recommendation.  I have heard to stay away from the high priced plugs and stick with the original equipment also should I be using regular gas?

ANSWER: David,
Use the regular plug nothing fancy. They last a long time and are reasonably priced.

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QUESTION: Should I be using high test or regular gas.  The car did not come with an owners manual

Answer
David,
This is from Volvo:  Octane rating :

Volvo engines are designed for optimum performance on unleaded premium gasoline with an octane rating AKI of 91, or above. AKI (ANTI KNOCK INDEX) is an average of the Research Octane Number, RON, and the Motor Octane Number, MON. (RON + MON/2).

The minimum octane requirement is AKI 87 (RON 91).