This is loading up on longer intervals that focus on the mile...
OP only mentioned his mile time, so maybe this is the ticket.
"my best advice" ran 1:56 800m and 9:22 3200m, and I would say there is very little difference between the two, and both are consistent with his 4:18 1600m (or 4:16 1600m, because he claimed a 4:18 mile).
The training that I advocate will greatly improve your 800m time, which will impact significantly on your mile. I didn't have sports my senior year, yet in an April open race, I beat runners who 6 weeks later ran 1:51 and 1:52 for a half (1:50, 1:51 for 800m). In two May open races, I twice went out in 55 and 1:24 to finish in 1:53+ for 800m.
I was also expected to run a very fast mile. Instead, I ran 3:58 1500m for open meet in May (3:16 , 42 last 300). A few weeks later, I ran a 3:56.11 (3:13, 43, 27 for last 200m) and won easily. If pressed, I would have run 3:54+, (3;13, 41, 25.5 last 200m).
I did run a slow 800m that summer (1:34 at 600m, sub 24 last 200m) and won.
Either system will produce fast mile times.
I guess it depends on how OP views himself as a runner.