What Oil do you use? (archive)

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- I have to say before I ask this question that this may be one of the most controversial subjects known to man no matter what the car etc. What oil do most of you use?

First of all, I truly don't know what the 10/20, 10/30, 10,40 or 20/30, 30/40 or 20/50 means etc. I have heard so many different explanations over the last 30 years that I am still confused, including explanations from oil company executives, racing car mechanics, good old engine rebuilders, parts people, Service managers, Oil distributers, refinery engineers, additive experts, scientists etc. etc. Rarely do I hear the same explanation twice or maybe I just don't hear it correctly. I do know for a fact that racing engines are built with looser tolerances in most areas and use thicker oil, meaning straight 40 weight, straight 50 wt. and others.

I know that a new passenger car engine used to be built with tight tolerances and needed 10 wt oil to properly lubricate the engine when new until the tolerances wore down and then a person would naturally go to a thicker oil like some version of 20 wt. Then when you got somewhere around 75000 miles it was always a good idea to switch to 30 wt to again accomodate the wider tolerances.

Also, most people think that the second number in a multi-viscosity oil means that the oil gets thicker when it gets cold or hot? But, I doubt very much if oil can get thicker when it gets hot. Some people think the second number means that its thicker when cold and then when hot thins out to the first number.

Some people say that the second number means that the oil will stand up to it's original wt viscosity named in the first number as the engine heats up. Most people don't know and just buy one that sounds good. Must be better right" if it has two options in the same oil and a slash inbetween. Hmmmmmmm

Some people think that the oil for a new engine is the best oil to use also in an old engine because whats best for the expensive new car is better for the older car. Most people don't realize that there are ratings other than the wt. numbers that establish how the oil holds up like cc, cs, cg, sr, and so many others. There may even now be an established governmental rating system, seems like I saw one at the parts store recently so that all oils must use the same rating system now just like movies. Gr- rated, R- rated, x-rated etc.

Some people think that there are many different manufactures of oil in the world, but I have been told that there are only two main makers of oil and that all the different brands buy from them and put their name on the can. Thats a great little story. I wonder what the actual truth is?????

At the moment my car (9i 850i) has approx 75,000 miles and my natural instinct is to put 30 wt in it with a couple of additives in it such as "Risloan (sp)an old timer" that I have always used and I have always gotten the max of miles out of my engines using that. But I always always used STP in later years to add some viscosity or slip, and I have always changed my oil and filter every 1,500 on every car that I own.

Everyone knows that BMW tells everyone that you don't have to change oil very often, but I believe that clean oil is better no matter what make the engine. I suppose this discussion could now move into filters, and then into additives.......almost scary isn't it. Right now I am actually using Castrol 20/50 synthetic oil mixed with regular oil, and of course Risloan and STP additives. Sounds good to me.
Lord I get tired thinking about it.
Kurt

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