Best longest lasting and most protective engine oil

What’s the best (longest lasting & most protective) oil should I use in my 2005 Chevy Uplander? Conventional or semi-synthetic, or fully synthetic? And why? Also, the weight? 5W30 or what?

Thank you

Full Synthetic oil is the best longest lasting and most protective.

Oil Specification 2005 Chevy Uplander

Engine Oil Capacity with filter included is 4.5 qts. Recommended oil is API – SAE 5W30.

Use oil that meets GM Standard GM6094M. For areas of extreme cold, where temperatures fall below -20F, it is recommended a SAE 5W30 Synthetic oil or SAE 10W30 oil. Both will provide easier col starting and better protection for your engine at extremely low temperatures.

Information Source: Mitchell1 Auto Repair Manual – online access for just $19.95

What to look for

When choosing a recommended oil it may seem there are too many choices. And your not wrong. But a quick look at the label on the oil container will let you know if it meets GM requirements. Make sure you see the API – SAE certification as seen in this example photo.

I looked it up for you if you would like to purchase. This is a 4.73 qt container so it will take care of the 4.5 qts. you need to change the oil. Take note, you will want to ad the oil filter also because the order needs to be $25 for free shipping and you probably are gonna want to change the oil filter at the same time.