I have a 01 Corolla (with an 7AFE engine not the 1ZZFE) with 285k miles. It´s burning 1 qt of oil every 1300 miles which is acceptable for me. I can get a Synthetic 5w40 Oil almost at the same price of the Dino HDEO 15w40 oil that I´m currently using, the HDEO is API SL rated and I can get two main synthetics with the following ratings: - PDV 5w40: API SM, ACEA A3/B3 04, MB 229.3, VW502/505, BMW Longlife Oil 01 - Venoco 5w40 & 10w30: API SN My questions are: Would I see any benefits using the Synthetic 5w40? My coldest starting ambient temp is 68 °F, so the 15w40 isn´t that thick at that temp. Would the 5w40 increase the oil consumption? My guess is that the 5w40 would have a lower NOACK than the HDEO 15w40, I think the oil burning is being caused by the rings, valve seals are almost new and there aren´t any leaks. I don´t know how NOACK would affect oil consumption in this condition. Would the 5w40 Synthetic harm my engine for being so thin? My car used Dino 20w50 98% of its life, this will be the first time in something that thin.