If you wax — ZFC-recommended path. Apply a top immersive wax pre-ride and ride it through. 160 km sits well inside every major immersive wax's single-application life — the baseline scenario for comparison. Ride through any surprise shower; tarmac rain is water, the wax handles it, and 160 km is too short to warrant the chain-stripper reset that oil-over-wax demands.
If you're on oil — pragmatic equivalent. Pre-ride application of your usual oil is plenty. 160 km is the baseline test of whether your application technique is working — if you're regularly topping up at this distance, your application needs work (more oil per link, longer dwell time, then wipe off the excess).