On a slightly different subject ...
In a previous life at another airline, we had a policy of shutting down the #3 engine after landing (this sometimes morphed to shutting down while on the high speed turnoff) on our 727's. It wasn't an "official" fuel saving measure but we were easy to convince that saving a little bit of gas was good for everybody's future.
Long story short ... we also changed more #3 engines. Was it because they didn't get adequate cooling time?
Did we really save any money in the long run? Enquiring minds want to know ...