Oil is SO low cost compared to ANY engine part. Be aware that new EPA rules requiring 'oxygenates' and Congressional inaction have forced gasoline blenders to use ethanol a lot. This radically changes the crankcase chemistry. The very low TBN value of the used oil test (around 1.0) is testament you werr on the ragged edge of engine corrosion, and probable getting some in the piston ring belt area.

If you want the engine 'as new' for many miles, cut the oil change interval to 5K miles and use a premium 'dino' oil if you don't want to spend the money. However, IMHO, this is false 'economy.' How much does gasoline for 5K miles cost? $700?