Posts: 742
Location: Grand Rapids MN | Raider you're going to hear a lot of different answers to this but I thought I would put out some insight. First thing to check is your owners manual and see if there is only one recommended oil or if they recommend an oil or another brand that meets a certain specification. There are occassions that there is some special formulation that is required but generally you can buy different products. Now here's where it gets a little deeper. When in doubt most people buy what ever brand oil from the manufacturer of their motor. Mercury oil for a Mercury engine for example. But remember Mercury doesn't make oil, they make engines. Mercury buys an oil from a supplier and has their name put on the package. In order to make money they may not buy the most premium oil out there, so you could not be receiving as high of quality oil that is justified by the price. Unfortunalely oil companies are not forced to disclose any quality specs or formulations on their oil, they just have to meet general specificiations which just tell you that an oil is compatible with a certain vintage engine. So there really isn't any information for you to get a hold of to make a good decision. That's why it's difficult for people to go outside the manufacturer brand name. And I don't blame them one bit. There is some information floating around out there but you have to know what you are looking for and looking at. Here's how oils are broken down.
Group I - is a conventional oil that has minimum refining. These are oils used back in the 1940's-1970's. Solvents were added to try to extract some of the aromatic rings. These rings allow oxidation and other oil breakdown modes. Don't see them much anymore.
Group II oils - are conventional oil that is put through a hydrotreat process. This is 1980's technology and what we see most today for conventional oils. These are further refined to remove more waxes & contaminants, control viscosity, and also further removed rings.
Group III oils - are a conventional oil that is put through a hydrocracking process. These are considered synthetic lubricants after a court battle was won between Mobil 1 and Castrol. This process breaks down some of the polymers to control polymer length, size, and structure. This is how they were able to say it was 'synthetic' because they changed the chemical properties and in doing so was considered 'man made' polymers. Still some waxes and aromatics remain but these are very good oils and highly refined. Most synthetic engine oils are this group.
Group IV oils - considered 'true' synthetic oils. These are 'man made' polymers, no crude oil was used. These engine oils are typically made of a PAO (polyalphaolefin) base synthetic and a co-base ester synthetic (either a diester or polyol ester). These have no waxes as found in crude/conventional oils and no aromatic rings. A PAO is completely saturated which means it does not like to mix with anything. That is why the ester co-base is used to disolve and hold the additive package. That is why they have higher temperature stability, water demulsification, and just a number of added properties. But synthetics cost more so that is the trade off.
There are only a few manufacturers of a Group IV oil on the market just because it is more cost effective to make a Group III and sell it a higher price like a Group IV. I'm not saying that a Group III isn't a good oil and not worth the money but for me I would rather pay the same price and receive a PAO. Mobil 1 and Amsoil are the only 2 that I know of that still make a PAO synthetic oil. For what we pay for boats and vehicles and how little capacity of oil they use it's worth spending the money for a good oil. If you have to change oil frequently because of other factors then it may be wiser to by a cheaper oil. A good maintenance plan goes further than buying an expensive oil.
I know this was more than you were asking for but I've seen a number of posts about this stuff at other sites and it gets ugly. Some are a Chevy guys other Fords, well the same goes for oils, some like Mercury, Valvoline, what ever and turns into a peeing match.
Hope this helps some!
Edited by Targa01 6/8/2007 12:46 PM
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