As 'religious' as people get about oil brands and viscosity, it's more of an art than a science. I don't think that it's even possible to buy motor oil that doesn't 'meet or exceed' ASE lube specs.
In nominal engine performance scenarios, the quality of oil comes into play during:
- engine startup.
- short driving trips where the engine and oil do not warm up fully.
If you garage your car, you've got a 20-30 degree advantage on the outside weather in the winter (assuming a cold weather climate of course). If you always drive 10 miles or more and make sure that the engine gets fully warmed up to drive out any accumulated condensation, etc, etc, you are also covered. These two conditions probably account for most of the engine wear people see over time.
I'm NOT accounting for engine/component or design failures like head gasket or water pump failures that may contaminate the oil. Pretty much no oil will cover your ass in those situations. Same thing with a cooling system failure that runs engine temps way above spec. All oil 'bets' are off in the case of internal failures.
As far as going 12 months between changes, it's probably not a good idea with aluminium block engines. Remember that in addition to lube, oil cleans and cools your motor. Combustion by-products, including acidic compounds, accumulate in the oil and no filter will get them out. Sure, changing the filter (espec if you use an oversized filter or something really big from www.permacool.com
) will get you a new quart of oil from time to time. But you are only taking a quart or 1.5 quarts out of the system on a filter change. Not enough to really keep things clean.
Remember that 'just sitting there' you'll be getting moisture condensation in the engine. That water will react with the metals and the oils no matter what you do.
Done yourself, an oil change is less than $30 even with Mobil1. Done 3-4 times a year regardless of mileage it's cheap insurance.