is yours a stick or auto? and by short trips do you mean 1 or 2 miles? or longer? do you let it warm up for a long time before you drive? it may have 10w30 oil in it (which is factory weight) however it states in the manual that 5w30 can also be used i would suggest 5w30 i even use that all year round in the texas heat as 5w30 pumps up to the top end faster when cool so it 1. will lubricate better while cool and 2. will help your mpg as the oil pump will be able to pump more oil quicker and will not have to work as hard, i notice more consistent and better gas mileage on 5w30. also use synthetic as it will keep your engine cleaner longer(this is a touchy subject but i can attest that it has worked in every car i have owned) and a good name brand oil filter. if its really cold you may see if you can find 0w30 (mobil and castrol make it in synthetic) for winter (mobil even says warranty for 5w and 10w30 applications)