22-06-09, 02:22 PM
Scusa ma un buon multigrado minerale no?cambiato ogni 5000 o 6 mesi?In tutti i v8 ho smpre messo del minerale cambiato ha intervalli (relativamente brevi), e non ho mai riscontrato nessunissimo problema anche in usi gravosi. 
The question of phosphorus and zinc.
Phosphorus (a component of ZDDP - Zinc Dialkyl-Dithio-Phosphate) is the key component for valve train protection in an engine and 1600ppm (parts per million) used to be the standard for phosphorus in engine oil. In 1996 the EPA forced that to be dropped to 800ppm and then more recently (2004?) to 400ppm - a quarter of the original spec. Valvetrains and their components are not especially cheap to replace and this drop in phosphorus content has been a problem for many engines (especially those with flat-tappet type cams). So why was the level dropped? Money. Next to lead, it's the second most destructive substance to shove through a catalytic converter. The US government mandated a 150,000 mile liftime on catalytic converters and the quickest way to do that was to drop phosphorous levels and bugger the valvetrain problem. Literally.
In the US, Mobil 1 originally came out with the 0W40 as a 'European Formula' as it was always above 1000 ppm. This initially got them out of the 1996 800ppm jam and knowledgeable consumers sought it out for obvious reasons. Their 15W50 has also maintained a very high level of phosphorus and all of the extended life Mobil synthetics now have at least 1000ppm. How do they get away with this? They're not classified as energy/fuel conserving oils and thus do not interfere with the precious government CAFE (corporate average fuel economy) ratings. (See my section on the EPA and fuel economy in the Fuel and Engine Bible for more info on this). This also means that they don't get the coveted ratings of other oils but they do protect your valvetrain. The same rule of thumb is true for racing oils like Royal Purple - because they're not classified as energy / fuel conserving, it would seem they still contain good quantities of ZDDP.
[url="http://www.carbibles.com/engineoil_bible.html"]http://www.carbibles.com/engineoil_bible.html[/url]
The question of phosphorus and zinc.
Phosphorus (a component of ZDDP - Zinc Dialkyl-Dithio-Phosphate) is the key component for valve train protection in an engine and 1600ppm (parts per million) used to be the standard for phosphorus in engine oil. In 1996 the EPA forced that to be dropped to 800ppm and then more recently (2004?) to 400ppm - a quarter of the original spec. Valvetrains and their components are not especially cheap to replace and this drop in phosphorus content has been a problem for many engines (especially those with flat-tappet type cams). So why was the level dropped? Money. Next to lead, it's the second most destructive substance to shove through a catalytic converter. The US government mandated a 150,000 mile liftime on catalytic converters and the quickest way to do that was to drop phosphorous levels and bugger the valvetrain problem. Literally.
In the US, Mobil 1 originally came out with the 0W40 as a 'European Formula' as it was always above 1000 ppm. This initially got them out of the 1996 800ppm jam and knowledgeable consumers sought it out for obvious reasons. Their 15W50 has also maintained a very high level of phosphorus and all of the extended life Mobil synthetics now have at least 1000ppm. How do they get away with this? They're not classified as energy/fuel conserving oils and thus do not interfere with the precious government CAFE (corporate average fuel economy) ratings. (See my section on the EPA and fuel economy in the Fuel and Engine Bible for more info on this). This also means that they don't get the coveted ratings of other oils but they do protect your valvetrain. The same rule of thumb is true for racing oils like Royal Purple - because they're not classified as energy / fuel conserving, it would seem they still contain good quantities of ZDDP.
[url="http://www.carbibles.com/engineoil_bible.html"]http://www.carbibles.com/engineoil_bible.html[/url]
