Unexplicable Power Boost

I second the breaking in theory. I know for fact that with my Wife's Mother's diesel VW Jetta, it actually said in the manual that over the first 20-30k, the engine would slowly build up more torque and improve in fuel economy, which makes sense because diesels are very high compression engines and any ease in the parts moving would be noticeable. The same is true to some extent with gas engines.

 

I noticed when it warmed up here in Nevada, my power went up and my fuel economy went from 19 mpg to 21 mpg. It must be the fuel.