I think most of the issue is lubricity, but I have to wonder that they refiners have other stuff they can use for lubricity.

Remember when they took lead out of gas, you had to run hardened seat and valve guides or they would wear out fast.

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1981 300D 147k
1998 VW Jetta Tdi 320k
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1979 300D 234k (sold)
1984 300D "Astor" 262k(sold)
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I love the smell of diesel smoke in my hair