Quote:
Originally Posted by BillK
I just changed the oil in mine today and it definitely needed it! The oil looked and felt like black water. I can't imagine this stuff lasting until 10 k miles, let alone the old interval of 15k miles. I'm glad I read this thread because 7 quarts is the correct amount
42pilot, you mentioned using rotella oil in the future, but is it rated LL04? I'm going to stick with BMW oil until the warranty expires and continue 5k intermediate oil changes but when the warranty expires, I was thinking about either Pentosin 5w40 or Motul x-clean5w40 as they are both LL04 rated. I'll go with 5w40 because I don't like how this oil felt too much like water. Whenever I change my oil, even with dark oil, it still feels like oil between my fingers, but this stuff was like water. I don't like it.
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LL04 simply means its a good extended-change oil. You stated you wouldn't wait the 10k miles, like me, between changes so why worry about using an oil approved for extended oil changes. In addition, Rotella T6, if filtered correctly, can last as long if not longer than any of the other quality diesel oils and this brand has hundreds of millions of miles of proof behind it's performance. But performance (lubricity, shear strength, viscosity, cleaning, etc) is not the issue here - filtering is.
Diesel fuel burned in an engine creates soot. Soot, larger than 4 microns becomes an abrasive. If you burn 200 gallons of fuel, you will roughly introduce an ounce of soot into your oil. You need to filter that out as this is the primary reason for engine wear in diesels.
No doubt lubricity, shear strength, detergents and so on are very important to the engine and the complicated exhaust system we need to run. But the whole reason I change my oil every 5000 miles is because of the soot issue.
In addition, I use the lightest weight oil I can. I cannot measure an oil's lubricity and shear strength using my fingers. These two issues tell you when the oil is worn out. Most high performance engines and race teams (including Formula 1, NASCAR, top fuel engines, etc) use 0 weight oil because it works and works really well without robbing horsepower from the engine-driven oil pump. It cools better than heavier weight oil, shear strength is equal to heavy weight oils, it removes crap from the cylinder walls left by combustion and it has very high heat capabilities. To top it off, a lighter weight oil will fill all the oil galleys in the engine on start-up much faster than a heavy weight oil. This will increase the life and performance of any engine.
The old school of thought, and I mean old school, felt as if heavy weight oil lubricated better, and it stood up to heat better. Older guys also thought heavy weight oil kept your oil pressure higher, which it did, but at the cost of horsepower, inefficient cooling, slow cranking in cold weather, etc. When I built Porsche motors, I used to shim the pressure relief valves to increase oil pressure so the owner wouldn't freak seeing an idle pressure of 10 or 15 psi. As long as there was a film of oil between the rotating or reciprocating parts (no metal to metal contact), you're golden. Higher RPM and higher pressure nearly ensures no metal to metal contact since fluids are not compressible. Anyway, today's engine tolerances are built for lighter weight oils too.
With all this being said, use the oil you are comfortable with. You own the car and are responsible for it.