I might be pushing my luck but on my 325i e-30 I go about 7500 on synthetic. No reason to regret it so far - been doing it from when I got it (214K) to the present, 303K.

Also, I dropped down to mid range gas (89 octane) a few years after I had it, and about a year ago, went down to regular (87 around here) on the advice of another MS shop member. No pinging, so sign that it was a mistake . . . so far.

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Te futueo et caballum tuum

1986 300SDL, 362K
1984 300D, 138K