Hampshire 451 ( Rossouw 120*, Vince 103, Onions 5-96) and 66 for 2 lead Lancashire 411 (Vilas 134, Davies 115, Clark 82) by 106 runs
Division One strugglers Lancashire and Hampshire look destined to play out a high-scoring Specsavers County Championship draw at Emirates Old Trafford.
With Lancashire and Hampshire both in the bottom three neither are likely to have achieved much headway by stumps on the final day, although Hampshire may be the happier, having avoided any morale-affecting defeat ahead of Saturday's Royal London Cup final against |Kent.
The Red Rose county, who have found runs hard to come by this summer, put in a solid performance on a flat pitch as the batsmen continued to dominate.
Then a wicket apiece for Tom Bailey and Graham Onions kept Hampshire in check with time running out for them to build on their slender lead and force a win.
Jimmy Adams was trapped on the crease by Onions as he fell lbw for four. Following on from his century on the opening day, Hampshire captain James Vince was then strangled down the leg-side off Bailey for 18.
Lancashire began the day on 140 for 3, still 311 runs in arrears. But Davies and Vilas put immediate pressure on the Hampshire bowlers.
Vilas reached a 114-ball half-century with six fours. The pair kept the scoreboard ticking over and brought up their 100 partnership.
Davies notched his maiden first-class ton of the summer and the fourth of his career off 176 balls, but he was only able add 15 more before needlessly gifting Rilee Rossouw a catch at gully off Ian Holland (208-4).
The wicket of Davies brought all-rounder Jordan Clark (81) out to the middle to join Vilas, and the 27-year-old played a perfect supporting role, allowing the South African to advance impressively.
In the opening over after lunch, Vilas reached his fourth century for Lancashire off 169 balls having hit two consecutive boundaries and 16 in all.
The fifth wicket pair looked to bat their side into the lead, but Vilas was trapped lbw by Kyle Abbott having faced 216 balls and hit 20 fours.
Clark, who shared 112 with Vilas, was left to marshall the tail with Lancashire still 131 runs behind, and a seventh wicket partnership of 58 with Arron Lilley boosted their cause.
But Lancashire, in the search for quick runs with the follow-on now out of the equation, lost their final three wickets for 17 runs as Stephen Parry and Bailey both fell for six. Sandwiched in between, Clark fell was run out by Vince.