<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Tom, F&L GoR:
Hi.
US fair trade laws prevent an OEM product recommendation from being a requirement, so this is really a technical specification set by the OEM, and any brand name use is a marketing effort by one of the products that meets the requirement. In this case, other oils do meet the DaimlerChrysler factory fill oil spec, but Mobil has decided to pay extra so their product is named.
As such, the technical spec probably doesn't require nor specify a synthetic, rather meeting certain engine tests and chemical tests. A synthetic isn't automatically better, mineral oils will do fine with the proper additive package. Which is better? That's asking if a strictly controlled diet is healthier than taking vitamins.
Synthetic base oil is a very poor solvent (unlike mineral oils, so this is actually a plus for mineral formulations) and in rare cases, it allows seals and elastomers to "dry" or shrink. In other rare cases, the rubber material is simply incompatible with the synthetic base oil and it swells. In recent years (about 15...) the only problem engine was a Mazda model, all other OEMs had seals made of "good" material, so not to worry about leaks.
The real advantage of a synthetic is the viscosity range - it acts like a thinner oil in the cold and a thicker oil when hot better than mineral oils. Therefore, you'll find an SAE 5W-40 synthetic, but not mineral. But then the oil marketers found people didn't recognize that "set" of numbers, so they've since made synthetics in 5W-30 and 10W-30, taking away (not providing?) the big advantage. Another marketing decision.
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