I was picking up some Motomaster Formula1 5W-20 at the cheapest price I've ever gotten 5W-20 - $8.39 for 4.4L - and I noticed an oil recommendations card displayed on the front of the oil rack. Here's their advice: Season: Winter Oil Grade: 5W-30 Reason: Reduce Engine wear at startup. Season: Summer Oil Grade: 5W-30/20W-50 Reason: Maximize fuel economy. Season: Year-Round Oil Grade: 5W-50 Reason: Best low temperature performance. At least they had a disclaimer at the bottom advising you to follow manufacturer's recommendations.