Interesting thread ... from a petrol/diesel compression perspective.
As to why petrols hold better than diesels : -
Maybe it's because petrols have a butterfly, which prevents air being sucked in past the compression rings - whereas diesel engine speed is controlled purely by fuel injection, with the air intake effectively open to the atmosphere.
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S80 D5-S manual (facelift) MY04 (avec V70 driver's seat)
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