Posted by Gordon Maney on Wednesday, October 10, 2007 at 07:16:01 :
In Reply to: Yes and no............... posted by Todd Wilson on Tuesday, October 09, 2007 at 00:31:55 :
Oil is marketed to end users by major refiners, such as Shell, blenders, such as Wolf’s Head, and retailers, such as K-Mart.
Shell retrieves crude from the ground, refines it, blends it, puts in additives, packages it, and sells it. Blenders buy blending stock from refiners, mix it, put in additives, package it, sell it. Both of these categories are subject to API and SAE requirements. Furthermore, lubricants are typically produced to meet mil-specs, as no refiner or blender wants to miss out on the possibility of sales to the government in quantity.
The last thing to consider is what I have called the green bean analogy. The Jolly Green Giant packages green beans in cans that say Jolly Green Giant, and also in cans that are labeled with a variety of other brands. They are all the same beans. Beverages are the same thing; milk and juices with name brands are put into packages with a myriad of brands. That is called co-packing. K-Mart oil is co-packed, using the beverage metaphor, and is someone else’s oil that says K-Mart on the can.
My point is that there are not so many different oils as there are brands, and they are all meeting the same specs. What I always told my students when I was a vocational automotive instructor was that you identify your viscosity and API service classification and then shop by price. Mixing brands and bases [asphaltic versus paraffinic] is irrelevant, as the refining process takes them past any differences in the crudes. Paraffinic crudes have their paraffin removed during the refining process. That is where the paraffin came from that grandma poured in the top of her jelly jars.
If you research it, you will discover that paraffinic crudes yield blending stocks that are naturally better in terms of viscosity index. That is great, but additive groups are the great leveler, ultimately, and you will change oil before that goes away, or at least you should, if you care about oil performance and engine life.
Any motor oil will have its additives depleted while in service, and if run long enough, the entire additive group will be depleted and no longer functioning. Having said that, oil change intervals have several purposes, that being one, maintaining additive group integrity.
Due to the practical influence of API and SAE requirements, along with the fact that there are not so very many truly different oils, if you change your oil, there is not a nickel’s worth of difference between any of them.
Also, just to stir up the hornet’s nest a bit more, changing brands has no effect at all. You will find people who say it does. “Uncle Marvin’s old Nash blew up right after we switched from Valvoline to Pennzoil, it was that oil for sure.” ....and you can’t convince people like that otherwise. But those are just stories.
My thinking on this is not simply stuff that I came up with while sitting around the campfire staring at the coals. It is from conversations with API personnel I have had opportunity to speak with over a period of years while I was an automotive instructor.
Buy the best API service classification you can, and put a lot of thought into the viscosity rating for your application, and then buy what is on sale, by the case or in gallons, as that is what will give you the best deal.
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