From the latest issue of Corvette Enthusiast magazine, they had an in depth look at today's oils.
Quote:
"The di-thio in zincdithiophosphate means for every phosphorous there are two sulfur molecules", Red Line Synthetic Oil Corporations's Vice Presient and top petrochemcial engineer, Roy Howell, told Corvette Enthusiast. "Sulfur is probably more importan than zinc and phosphorus
The cam and lifter wear surfaces are rich in iron and sulfur with a lesser amount of phosphorous. The ZDP decomposes into a soft, thin film of iron sulfide and iron phosphate which prevents iron adhesion, or welding. The zinc doesn't do much. If you look at photomicrographs of cams and lifters, there's hardly any zinc coating, but there's a lot of iron sulfide coating and some iron phosphate coating.
"With this process, you trade adhesive wear for chemical wear. If you didn't have these soft films, which prevent iron from touching iron - if you didn't have something in the middle, the you'd get adhesive wear - welding - and that iron to iron weld would pull "chunks" out of the lobe and follower. What makes zinc dialkkyldithiophosphate unique is its precise thermal decomposition temperature which can be manipulated by changing the composition of the the organic alkyl group attached to the the phosphorus. If it decompoeses at too low a temperature, chemcial wer would occur where it is not needed, but if it occurred at a higher temperature, then some adhesion or welding, would already be taking place..
There are a lot of different sulfur compounds", Howell continued, "but this one has "precision-controlled" decomposition. In many of the others, the sulfur and the phosphorus are much more loosely bonded. There's a bigger "range". It might partially decompose at a lower temperturea and finish at a a higher temperature, or maybe decompose only at a higher temperature. However, with ZDP-boom at 400 F, it starts to thermally decompose, then react with the surface of the lobe and lifter to form those almost monomolecular soft films. As the lobe rubs against the follower, that film will get rubbed off, and in the next revolution, the same thing happens again."
Rest of the article is a good read about ZDP and today's engines. In part 2, they are going to cover camshaft installation, break-in procedure and review specific oil choices for your vette.
More importantly though, they talk about how tough the Seq IIIG test is and how durable today's oils are. Wear really isn't an issue with today's engines.
Quote:
"The di-thio in zincdithiophosphate means for every phosphorous there are two sulfur molecules", Red Line Synthetic Oil Corporations's Vice Presient and top petrochemcial engineer, Roy Howell, told Corvette Enthusiast. "Sulfur is probably more importan than zinc and phosphorus
The cam and lifter wear surfaces are rich in iron and sulfur with a lesser amount of phosphorous. The ZDP decomposes into a soft, thin film of iron sulfide and iron phosphate which prevents iron adhesion, or welding. The zinc doesn't do much. If you look at photomicrographs of cams and lifters, there's hardly any zinc coating, but there's a lot of iron sulfide coating and some iron phosphate coating.
"With this process, you trade adhesive wear for chemical wear. If you didn't have these soft films, which prevent iron from touching iron - if you didn't have something in the middle, the you'd get adhesive wear - welding - and that iron to iron weld would pull "chunks" out of the lobe and follower. What makes zinc dialkkyldithiophosphate unique is its precise thermal decomposition temperature which can be manipulated by changing the composition of the the organic alkyl group attached to the the phosphorus. If it decompoeses at too low a temperature, chemcial wer would occur where it is not needed, but if it occurred at a higher temperature, then some adhesion or welding, would already be taking place..
There are a lot of different sulfur compounds", Howell continued, "but this one has "precision-controlled" decomposition. In many of the others, the sulfur and the phosphorus are much more loosely bonded. There's a bigger "range". It might partially decompose at a lower temperturea and finish at a a higher temperature, or maybe decompose only at a higher temperature. However, with ZDP-boom at 400 F, it starts to thermally decompose, then react with the surface of the lobe and lifter to form those almost monomolecular soft films. As the lobe rubs against the follower, that film will get rubbed off, and in the next revolution, the same thing happens again."
Rest of the article is a good read about ZDP and today's engines. In part 2, they are going to cover camshaft installation, break-in procedure and review specific oil choices for your vette.
More importantly though, they talk about how tough the Seq IIIG test is and how durable today's oils are. Wear really isn't an issue with today's engines.
