Suggest, yes. Require, no. The engine management systems will recognize the symptoms of running lower octane fuel and adjust the program to match. Spark is retarded to accomodate the lower octane fuel's disposition to predetonation. You will lose a little performance, but not much.
i have a 1991 lexus ls400 and when i start after it has been sitting all night it blows kind of...
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i have a 1991 lexus ls400 and when i start after it has been sitting all night it blows kind of thick grey smoke form the pipes for about 3 minutes but there is no overheating or sign of a head gasket problem but the check engine ligth just came on.