Rich running on start up isn't going to make that much of a difference to the amount of fuel that makes its way past the rings. It's a very slight increase above stoich', not turning the injectors to 100% duration. A modern car goes into closed loop very quickly.I broadly agree to this theory. The only two exceptions to this are:
1. If someone does a lot of short stop start driving/ city driving and no regular 50+ mile drives, then there is a lot of fuel dumped in oil and severe service instruction of 6 mths / 5K Miles needs to really be adhered to.
2. The engine is generally clean burn. If you see black oil in the first 5 K miles , checked through dip stick, then its worth changing the oil with a Engine flush added in. This only happens after 50K miles of driving in point 1 and oil changed every 10K miles.
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