Please explain why synthetic oil is the way to go. If you change oil every 3 to 6 months where is the benefit and why is Castrol full of crap. I am sitting on the fence as to which way to go and would appreciate your reasoning.
If you change your own oil, the difference in price is negligible, especially if you buy in 5-quart jugs at Walmart.
I am not going to go over all the benefits of synthetic (you can read that elsewhere), but I am absolutely convinced it is the way to go. Note that most Toyota and Honda vehicles now specify synthetic (or specify 0W-20 which is only available in a synthetic).
I will address the Castrol issue. Mac West is referring to the fact that Castrol (now owned by BP) developed a new class of oil that is severely hydrocracked (using very high pressure and heat). These Group III oils are sometimes described as synthesized hydrocarbons sold it as "synthetic" starting in about 1997. Mobil complained to the FTC and said that only Group IV PAO or Group V Esters could be called synthetic, and that Castrol was making false advertising claims. A judge ruled that Group III Severely Hydrocracked Oil had its molecular structure modified and was substantially different than Group II conventional oil and could be called "synthetic." Note that this only applies to the USA, and in many foreign companies, they still cannot call a Group III oil synthetic.
Since then, there have been more advances in hydrocracking technology, and Group III oils are now quite good in comparison to Group IV and V synthetics. And because of lower costs, most brands of synthetic sold in the US are either 100% Group III (not counting additives), or a blend of Group III with some Group IV/V components. Even Mobil 1 switched from 100% Group IV/V to a blend that has about 35% Group IV/V components (rest is Group III). Even Castrol Edge Extended Performance "may" have some of Group IV/V in it (regular Castrol Edge is 100% Group III).
Amsoil used to claim that they were 100% Group IV and V, but they now have three lines of oil, and only the most expensive line has any Group IV or V, and even now it uses some Group III.
Shell has developed a new type of Group III hydrocracked that uses natural gas instead of conventional oil. It is sold under their Pennzoil Platinum brand in the US.
In any event, even a 100% Group III motor oil is superior to any conventional Group II motor oil, even if you use a generic brand of synthetic (like Walmart Tech 2000). But a 5 quart jug of Mobil 1 at Walmart is only $25, so why bother with anything else. Most oil change places will allow you to bring in your own oil to use, which is usually cheaper than what they charge for synthetics.
Review Motor Oil Group Classification:
- Group I - Conventional Oil (less than 90 percent saturates) - no longer meets API requirements for new vehicle engines.
- Group II - Conventional Oil (more than 90 percent saturates) that is moderately hydrocracked. Most non-synthetic motor oil sold for vehicle engines is this group.
- Group III - Conventional Oil that is severely hydrocracked to create synthesized hydrocarbons. The vast majority of synthetic motor oils sold in the USA as synthetics are 100% group III (not counting additives).
- Group IV - Polyalphaolefin (PAO) synthetics - Used in some better quality synthetics such as Mobil 1 (along with Group III).
- Group V - Ester synthetics (not necessarily better than Group IV in all respects, and often used in oil additives)
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