I love synthetic oils, but I will say that I switched to it on a couple higher mileage vehicles and immediately developed some small oil leaks. I am not SURE, but a lot of people have acknowledged that the detergents in the Synthetics can cause small leaks to develop in higher mileage vehicles.

Not sure there is any truth or science to it, but it was my experience. Both the cars that did this to me were DOHC engines.

Amsoil does not recommend going beyond 5k between changes with ANY oil due to fuel dilution from the dpf system. I change every 10k on my 6.4, but it has dpf and egr delete. Before i deleted all the emissions components the oil seemed way overdue even changing at 5k. Looking forward to installing a dpf/urea delete on a friends 6.7 in the near future, can't wait to see what this motor is capable of!

What happens is Petroleum products over time can create "false" seals, aka buildup, and with the high detergent packages in the synthetics, those can start to be cleaned up and yes, may "open" up some leaks. So there is some truth to your statement.

Black doesn't mean anything. Oil turns black from heat and a chemical reaction with the metals. My father has a 2000 Excursion 7.3 with roughly 550000 miles on it. He uses AMSOIL 10w-40 with a Bypass Oil System and has only changed the oil 7 times. The ONLY way to tell if oil is good or not is do an oil analysis. Color doesn't mean squadoosh!

Actually they recommend 3x longer than OEM intervals with the new oil, or longer with oil analysis. Have you seen somewhere that they said OE intervals? I am curious, because that would be news to me.

The amsoil rep clued me in on the 5k mile interval with dpf systems intact. He did say that amsoil maintains lubricity longer even with the fuel dilution from the regeneration process.

Duramax
 

That's the beautiful thing about the 2011 Duramax. Minimal EGR cause emissions are taken car of with DPF and urea. The smartest thing they did was put a ninth injector in front of the DPF in the exhaust so they don't inject the extra fuel into cylinders during regen...no more diluted oil! I am sure Ford and Dodge will do the same.

Ford 6.0 PSD...every 3,000 miles.

But the truck is for tow only. Oil changes are only once a year when it goes in for a state inspection.

good point!! injecting fuel during the exhaust stroke to clean the dpf is what is causing the oil dilution not the egr. bypass both systems & you reduce potential failures considerably. if I owned a 6.4 or any other common rail diesel I would install an additional small micron fuel filter to protect the injectors & hp fuel pump & delete the egr & dpf systems. most catastrophic failures we see are due to fuel debris damaging the pump or injectors (mostly rust) EGR cooler failures & cavitation allowing coolant to enter the crankcase through the front cover. I wouldn't go past 5000 mile oil change intervals without deleting dpf & egr systems.

EGR & DPF systems are mostly separate from each other. EGR is used to cool cylinder temps to reduce oxides of nitrogen production. The DPF system with or without urea is is used to reduce particulates in the exhaust. both systems are strictly used to please the tree hugger crowd & both lower your mpg especially the DPF.