This will not be a short post - you've been warned!
Firstly, let's look at the statement about all oils coming out of the ground - UNTRUE.
There are petroleum oils (from the ground) and synthetic oils (made by chemists in laboratories normally of poly alpha olefins or esters) these are not the same performance wise as synthetics are by far superior lubricants because they are custom designed for the purpose for which they are intended.
Now, oil is made up of basestocks (75-95%) and addatives (25-5%) there are 5 different catagories, 1 being the lowest grade petroluem oil to 5 which is esters in the case of automotive oils.
1 and 2 are petroleum (mineral oil) basestocks
3 are petroleum oils that are "hydrocracked" which is the highest quality of petroleum based oil refining and often labelled as synthetic although from a chemists view they are not "true" synthetics as above. (Mobil vs Castrol)
4 are synthetics and are poly alpha olefins referred to as PAO.
5 are all other synthetics including esters
Basestocks are commonly blended and for example Magnatec is Group 1 and 2 with a small percentage of 5 added to give the polarity, esters are polar and all others are in fact inert.
That being said, this type of blending will not produce as higher quality oil as blending solely group 4 and 5 basestocks which are the best quality.
So, why use a quality oil?
To be frank, it's down to you. The fact is that ALL cars will benefit from the best quality oil and it's really down to a cost/benefit analysis on your part. To do this excercise you need to know some facts around the way oils perform over a period of time.
ALL oils shear (lose viscosity) with use due to an addative called VI Improver which in a multigrade is necessary to "fight" the thinning effect of heat on the oil. This addative is made up of heat sensitive polymers that uncoil as the engine temps rise but it is prone to shear which in turn means that the oil becomes thinner as these polymers break down.
So, the less of this that is used in a formulation the better as the oil will thin at a much slower rate. Synthetics (group 4 & 5) mentioned above are far more temperature resistant (thermally stable) than their petroleum cousins and therefore require little of no VI Improver to work as a multigrade which is why they are able to withstand longer drain periods.
As a guide, the following oil drain periods should be observed
Mineral oil 2000-3000 miles
Semi Synthetic 3000-5000 miles
Fully Synthetic (Group 4 & 5) 9000-12000 miles
When you weigh up the costs, a fully synthetic is in fact cheaper taking into account it's drain periods.
So, are all oils the same? The answer is catagorically NO!
You should take time to read this which is written by a top R&D Chemist who has forgotten more than I know, it's frank and factual and more importantly not a sales pitch!
A word of caution – You get what you pay for!
Below is an article written by John Rowland, Silkolene/Fuchs Chief R & D Chemist for 40 years.
Quote:
Costs of synthetics vary considerably. The most expensive are the “Ester” types originally only used in jet engines. These cost 6 to 10 times more than high quality mineral oils.
The cheapest synthetics are not really synthetic at all, from a chemists point of view. These are in fact specially refined light viscosity mineral oils known as “hydrocracked”. These have some advantages over equivalent mineral oils, particularly in lower viscosity motor oils such as 5w-30 or other oils with a low “W” rating such as 5w-50 etc and they cost about 1.5 times more than good quality mineral fractions.
We use several different grades of this base oil, where appropriate. This is the “synthetic” which is always used in cheap oils that are labelled “synthetic”. Yes it’s a cruel world, you get what you pay for!
Now, you may ask, why are these special mineral oils called “synthetic”?
Well, it was all sorted in a legal battle (Mobil vs Castrol) that took place in the USA about ten years ago. Sound reasons (including evidence from a Nobel Prize winning chemist) were disregarded and the final ruling was that certain mineral bases that had undergone extra chemical treatments could be called “synthetic”.
Needless to say, the marketing executives wet their knickers with pure delight! They realised that this meant, and still does, that the critical buzz-word “synthetic” could be printed on a can of cheap oil provided that the contents included a few percent of “hydrocracked” mineral oil, at a cost of quite literally a few pence.
So, the chemistry of “synthetics” is complex and so is the politics!
The economics are very simple. If you like the look of a smart well-marketed can with “synthetic” printed on it, fair enough, it will not cost you a lot; and now you know why this is the case.
But, if you drive a high performance car, or you intend to keep your car for several years, and maybe do the odd “track day”, then you need a genuine Ester/PAO (Poly Alpha Olefin) synthetic oil.
This oil costs more money to buy, because it costs us a lot of money to make, very simply, you always get what you pay for....
