Senegalese striker Diouf turned home a pair of clinical finishes at Leigh Sports Village to put the Reds firmly in control of proceedings, before Lingard and Keane added gloss to the scoreline in the dying stages.
Warren Joyce was able to name a strong, experienced line-up in his side's final outing of 2011, and it didn't take long for the Reds to forge ahead, as Diouf latched onto Darron Gibson's pinpoint long pass to head home.
Shortly after the half-hour, the lead was doubled as a surging run from Rafael, who completed 90 valuable minutes in his comeback from injury, culminated in the Senegalese slipping home a neat finish from deep inside the six-yard box.
The second period drifted at times, with United largely controlling proceedings, before a late surge made for a more emphatic victory.
Substitute Lingard popped up to secure victory from just inside the box with 10 minutes remaining, five minutes before Keane hammered home a deserved fourth to cap another sharp personal display and a fine team outing.
United: Amos; Rafael, M Keane, Fryers (Fornasier), Vermijl; Cole, Gibson, Pogba; Diouf (Petrucci), W Keane, Macheda (Lingard). Subs not used: Jacob, Thorpe.