Heavier oil is ok if the weather is warm. In Kentucky you don't get enough cold to worry about changing back in the winter. My 85' VW Golf Cabriolet runs 20W50 in the summer. But up here, when the real cold starts, I bring it back to 10W30 or it gets to thick to crank in the morning. I never ran heavier oil in my Escape even when the oil light started the flicker issue than 10W30.