Makes sense, the TSB says that the 5w20 oil will improve fuel economy.... and that's about it! Thinner oils create less drag (windage) on moving parts. You can run the original oil weight all day every day and nothing bad will happen. As long as it's a name brand oil you really cannot go wrong. It's only when you go into extreme racing applications that specific choices need to be made with lubricants, and not just the engine oil but every lubricant in the car. If it's street driven with occasional fun track duty, just send it. Hardly any of us are R&D'ing our cars here.
