Thot you said "DTE heavy"? That's a "recirculating" turbine oil, low/no detergent nor similar modifiers. Generally for non-pressured systems where there is no positive pumping nor filtration and nanoparticles are meant to be allowed to just drop-out, settle in a sump, STAY there until flush-month.
10EE "Round Dial" use both DTE Light (uber-precision spindle bearings, up to 4,000 RPM.. sometimes more) and DTE Medium (threading and surfacing gearbox), then Vactra #2, apron gearbox ++, and ways.
DTE "numbered", similar viscosity, modest detergent/suspension additives for where there iS a pump and filter. More common, medium & larger lathes to newer goods, yet.
Vactra #4 would be a heavy. LARGE mills, high mass, rectangular bedways not uncommon.
Gears would "pull" it and spread it from the least contact off a sump. Tacifiers help that, but it is "going to happen", regardless.
Presuming the bearings are rolling-element? I'd NOT expect Vactra unless they run woefully slow. "Skating" could be an issue.
Tacifiers are what they sound like. Sticky adhesives. Ergo ALSO bind surface DIRT.
So I don't use Vactra for waylube on my 10EE's, nearly a hundred years since it entered the room as one of the Standard Oil Company, New York - Vacuum (refined) "Gargoyle" tribe.
DTE "named" would seem better, your use? More especially so if Rambaudi specified it. They made some serious-large and uber-powerful geared milling heads for gantry mills, too - generally knew their stuff,