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Dyno oil will oxidize and wants to form a solid or a goo, depending how far things go. Heat, partially burn fuel blowby, NOX in the blowby all drive the oxidation of the oil. This is polymerization, just like paint drying. Fine metal wear metals act as a catalyst, just as 'Japan Driers' will accelerate the oxidation reactions in paint 'curing'. So, heat, blowby gases, wear metals and time are the factors. The 2.3 liter NA engines are a rather high 10:5 compression ratio, so heat, blowby and NOX all go up when cruising down the road compared to the 2.0 liter turbo at 9.3 compression ratio. But some turbo engines are sludged, but much fewer. I would not blame the engine, this an oil related issue. Cheap oils that meet the API spec may not be up to the task.
The advent of oxegenates in fuel, carries more reactive oxygen bearing materials into the engine oil. These may be a key factor in oil sludging.
The biggest factor is ignoring oil changes! I also think that the turbo owners are as a group more engine minded and take better care of such things, and they as a group more often use:
Synthetic oil: Synthetic oils were first developed to withstand the heat in jet engine bearings where dyno oil will coke up. A true synthetic will not coke up in the piston ring lands like dyno does. Newer engine designs have pistons with the top compression ring much closer to the top of the piston. This improves combustion, but the heat is much higher. So comparing to older vehicles is not going to help. I have doubts about group III highly hydrocracked dyno oils such as Castrol FakeTek(tm). I am not convinced that such oils will fair as well as a true synthetic like Mobil 1 which is a group IV or IV&V mix. So as long as the group III oils are over priced to match Mobil 1, you might as well get a true synthetic. M1 0W40 is there best oil. Delvac 1 5W40 might be as good or better, but hard to get and often quite expensive.
When piston rings sieze, the compression gets worse and the blowby gases increase and the oil gets worse. A cycle of degraded oil and accerating wear can accelerate the whole process with higher loads of wear metals.
You need a better oil to survive in these engines. Many newer high compression engines in the market place may have equal issues.
posted by 66.142.222...
, Thu, 5 Feb 2004 12:09:38
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