If thinner oil caused more wear over the long run it would most likely take longer than the warranty period to show up with a problem requiring warranty coverage. Of course abuse like using xW-20 for extended track days without an adequate oil cooler would be another thing. Normal street driving (no heavy towing, etc) might cause a bit more wear, but not enough to cause any major "failure", unless there was a lack of lubrication (ie, very low oil level, badly degraded oil due to lack of maintenance, etc ... or lack of oil flow due to an oiling system problem).