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Synthetic vs. Conventional - A guy at a party perspective ![]() Posted by Sondeen [Email] ![]() ![]() In Reply to: SAAB Talk Live: Synthetic Oil vs. Conventional - A lab owner sets us straight, Scott Paterson ![]() ![]() |
So a number of years ago I got talking to a PhD chemist at a party who spent most of his career with Mobil developing synthetic oils for diesel trucks. As the only two science types in the room (I an engineer) we meshed well and talked for some time. He told me all about what made synthetics better, I having recently bought a Saab, was all ears. Conventional oils begin as crude oil from the ground and are refined to remove everything you don’t want in there. You do your best to get the unwanted substances out and end up with mostly lubricating oil. You then can add various substances to improve the oil properties, but in the end you have to live with some level of junk that could not be refined out, it is a compromise, and that ultimately limits how the oil performs.
With synthetic, you build the oil from pure elements (I.e. carbon atoms), and add other modifying elements and compounds in just the ratios you want. In other words you synthesize it, building the oil to match a specific design. You don’t have to deal with leftover junk. Synthetics were originally developed for large commercial Diesel engines and aircraft engines, to allow for extended drain intervals. A trucking company wants the trucks on the road making money not in the shop getting oil changed. My PhD pal told me semis doing long distance hauling can typically run 20,000 to 30,000 miles between oil drains if running top quality synthetic.
The main advantage with synthetic oil in a gasoline engine is they take longer to break down, thus you can greatly extend drain intervals, and they can tolerate higher temperatures without forming coke (burnt solids) and sludge. Conventionals will lubricate just as well as synthetics over the short term, the trade off is you need to change them more frequently.
I can see why the guy in the video from Blackstone was not so hot on synthetics, his approach is to buy less expensive conventional oil and change it more often. That certainly works for most people in most cars, and has been proven out. But if your car can run the oil a bit hot in parts of the lube circuit due to inadequate turbo cooling or poor exhaust routing (og 9-3), synthetics will give an advantage. Also consider his perspective in testing, he is measuring the properties of used oil, with a quite random service lives. He is not trying to do controlled experiments to compare one oil type to another after testing in a fixed environment or trying to optimize the design of a synthetic oil through controlled tests and post test analysis. So l totally get why he says to buy an oil that meets API standards and change it every 5,000 miles, that will work for most basic cars out on the road today. But for my 9-3, I am sticking with Mobil 1.
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