My experience with OS engines is that they spit oil much less than other engines, both their 2-stroke and 4-stroke. OS 160 FX owners can attest to that.

4-strokes spit oil not only out of exhaust, but also through the breather nipple. Some new OS 4-stroke Surpass 2's have a line connecting the breather nipple to the intake manifold, so eliminating the oil that would have gotten out from the breather nipple.

Also, the type of fuel you use will make a difference in how much fuel getting spit out. Fuel with all-synthetic lubricant is less messy than those that contain castor. So for example, Wildcat Helimax w/ 16% all-synthetic lubricant would be less messy than Sig Championship w/ 10% castor + 10% synthetic. These are airplane fuels. Make sure you use the fuels that the OS car engine manual recommends.