Not necessarily, most warning lights come on at 5 or 10 psi, so they don't come on at idle when the engine's hot. At 50 mph, on full boost (turbo diesel ??) it might be making 20 psi but that won't be enough to keep Mr Big End Bearing happy for more than a second or so. There could also be a lot of air being sucked up into the oil galleries which is only marginally better than no oil.