Back to the bottom end question - My opinion is that the life of the bottom end is based on the frequency of the oil changes the first 100k miles - remember my opinion. A couple of examples - I owned a '91 Mazda van 4 cyl. and the radiator came apart at 125,xxx miles - the wife was driving and did not stop until the vehicle did. Anyway, I had changed the oil and filter every 3k miles. The cylinders still showed good signs of cross hatching and it did not use any oil. The damage was to the piston skirts and rings. No telling how many miles that vehicle could have gone and I am sure the guy I sold it to is probably still driving it with that engine (sold it at 155k miles). Another example is a Nissan truck I purchased new in 1986.5 (Nissan hardbody -4 cyl). Again, I changed the oil/filter every 3k miles and the painting company I sold it to (at around 80k miles if memory serves me correctly) is still driving it with over 280k miles showing on the odo. I will say it looked like heck and idled pretty rough. I seriously doubt if they have ever even replaced the timing chain in that vehicle.