For a time in the late 1940's a large share of Lionel's production was O-27 sets, cars and engines, because they were marketing at a lower price point to compete with lower-priced competitors.
O-27 track height was lower, I guess to use less material so as to be able to sell it for less. The O-27 wheels on all of their O-27 line had shallower flanges to run on the lower-profile O-27 track.
But- if you run on standard O-Gauge track of any description, the car (O-27 or O Gauge) should run fine on either O-27 OR O Gauge tubular, or Fastrack, MTH. etc. The only problem I have seen with O-27 cars that use "running shoes" to activate the couplers will (some of them) open the couplers running over O Gauge switches.
Just not the other way around: O-Gauge wheels with their deeper flanges, will likely "bump" on the ties of O-27 track.