Reasonably treated engines so commonly go over 300,000 and 400,000 miles that I'm not sure it proves much about the oil. For only 3 examples:
My Mazda went over 600K miles on whatever conventional 10W-40 was on sale.
My brother's '85 Jetta went well beyond 300K on the same.
His '95 Avalon is at about 340K on whatever synthetic 5W-30 is on sale.
None of those had oil-related wear problems.
My Mazda went over 600K miles on whatever conventional 10W-40 was on sale.
My brother's '85 Jetta went well beyond 300K on the same.
His '95 Avalon is at about 340K on whatever synthetic 5W-30 is on sale.
None of those had oil-related wear problems.
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