I changed my oil with 5w30. My mechanic said it's good for the winter months. I understand viscosity when hot and cold but it still seems kind of thin to me. I have a 1.8 gasser in the caddy that was swapped at some point. I know it's a 1.8 because the engine code under the 3rd and 4th spark plug begins with jh. I don't know the exact year or model it's from. I'll drive it a few times a week to work this falll but won't drive much this winter. I also thought older engines require thicker oil. Thanks.