[quoteSo you suggest just going with the NAPA Gold syn from the first oil change ]
You certainly can. You can drive from the dealership to the garage and change it if you like. Oils that fleets use a lot of and have great success with would be Rotella, Delo 400, and Delvac. These are dual rated oils unlike most of the oils you're familiar with. If you have diesels in the fleet, these can eliminate any confusion at the garage as to which to use. These are very robust base oils and come with a lot of detergents in the package to keep things clean. They are pretty tough oils as they are designed for fleet use. Might do a cost comparison to see if it's worth your money to change. Your NAPA store should be a stocking dealer.
Lloyd, my comments were more directed to the components, not the engine. That would be axles, transmissions, any of the other lubes. If you have arctic cold startups, look to the oil makers website and look for the CCS rating of the oil you are considering. CCS= Cold Crank Simulator. A lower number is better. This test actually simulates the cold start properties of an oil. It may surprise you as not all oils are the same at extreme cold despite having the same SAE viscosity rating. Synthetics do not always win this category. If you're attempting to stay in Dexos spec, just so I can say so, Dexos is a way that GM is milking the oil industry and the consumer is paying out the butt for it. Because of the extreme cost of getting Dexos certification, the oil companies are using the most expensive components in their formulations to get their money back. If you read the owners manual carefully, it states that if Dexos speced oils are not available, any API certified oil will do in the correct viscosity. Also, any supercharged engine should be running a heavier than normal oil. This is because a lot of the fuel gets washed into the oil under full throttle and it dilutes the oil. Most supercharged engines will run a 15-40 minimum or like the Mustang, run a 15w-50 oil to prevent the oil from becoming too thin with fuel. The 5w/15w-50 oils requires a synthetic base (high viscosity index) to make the viscosity spread otherwise they would have to load the oil with polymers (Lucas crap) and they are known to condense out of formulation causing sludge.