Mark Wood's five for 78 edged Durham closer to safety after they wrapped up their third victory in a row with just eight balls to spare, condemning title-chasing Nottinghamshire to a first four-day defeat of the season.
Alex Hales compiled a first century of the summer with 101 and Riki Wessels made 98 in an opening partnership of 168 in 42.1 overs as the hosts looked to be well on their way towards a target of 366 from 90 overs. But it was seamer Wood who played the decisive hand, removing Hales and polishing off the tail to complete a tense 16-run success.
Spinners Gareth Batty and Murali Kartik bowled Surrey to only their second victory of the season but it was a nail-biting affair against Middlesex.
The visitors fought hard to reach 245 in their second innings before going down by just eight runs at the Oval.
Batty took six for 83 - including the last wicket of Toby Roland-Jones for 17 after he and Tim Murtagh (25 not out) had added 48 amid great tension - and Kartik three for 91 in a marathon four-and-a-half-hour spell from the Vauxhall End.
Surrey finally wrapped things up just after 4pm to take 19 points and boost their chances of avoiding relegation.
But the spectre of relegation loomed ever larger for Lancashire as Worcestershire restricted them to only one batting point from their crucial clash at New Road.
Worcestershire, still with a game in hand, closed the gap at the bottom of the table after dismissing last year's champions for 216 in a draw that came down to a scrap for bonus points.
Gareth Andrew led the way with a season's-best return of four for 42 and Moeen Ali, who captured 12 wickets in last month's win at Old Trafford, polished off the lower order with three for 46.