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Old 12-09-2011, 08:22 PM
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JCL JCL is offline
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But other things aren't equal. I agree that a lower speed engine will have potentially less cylinder bore wear, but recall that the gasoline version is now turbocharged and gets its peak torque at a similar rpm to the diesel. My 535i reached peak torque at 1300 rpm, and I would expect the V8 to be somewhat similar.

Now add in the peak cylinder pressures from the diesel compared to the gasoline version. This will impact block fatigue, bearing loads, and thust loads on the piston and cylinder wall.

I know that piston loads increase with the square of engine speed, and only linearly with increased cylinder pressures, but the diesel always has higher cylinder pressures, and the gasoline engine is only occasionally at higher rpm.

All in all, I would call it a wash. There is no logic to the diesel lasting longer, but it shouldn't last any less time, either. And it isn't like the transmission, ancillaries, and electronics are still going to be working as new when the engine finally does give out.
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