This question is related to single/twin piston engine aircraft. After flying in a Cessna 152 and a Piper Dakota I have noticed that they both consume a lot of oil. Oil check is an integral part of the checklist. Pilots carry extra bottles of oil in the back. Why is this so? Especially compared to car engines that are 'similar' and do not require such regular top offs?
Automobile engines are not similar. They are liquid-cooled and therefore can be built to much tighter tolerances with regard to thermal expansion and contraction.
Air-cooled aircraft engines must deal with a large range of operating temperatures and oil is consumed due to the relatively looser fit of the piston rings.
As I think most folks here tend to be A&P's I'll add this. Aircraft horizontally opposed four cylinder engines also use specifically "asheless dispersant" oil because the oil is pumped to lubricate the top of the cylinder and a decent bit is burned in combustion. So yes, there is a line that can be considered "excessive" and that has a lot to do with wisdom in a small piston engine as opposed, to a jet where there is generally a one pint per hour limit, or something to that affect, where anything more than than that would require an oil consumption run. But as far as aircraft piston engines go, they do burn oil because they lubricate differently than an automobile engine.
'Air cooled engines' is a popular misnomer... oil does the primary cooling, with the fins on the cylinders only dispersing part of the heat. The oil, in addition to lubricating, draws heat away from high temperature points, like the cylinder heads, bearing surfaces on the crankshaft, and to a degree, the cylinder walls when oil splashes on them.
For a variety of reasons, oil/air cooled engines tend to consume more oil than water cooled engines, from the wider temperature range the engines experience, to the oil doing double duty.
In addition, the flat cylinder layout can result in some oil loss on startup, from oil pooling in the cylinders when not running, which doesn't happen in vertical or V cylinder arrangements that are typically used in automobiles. This is especially true of radial engines, which have some cylinders inverted, letting oil pool on the pistons when not running, leaking past and getting into the combustion chambers. That's why radial engines tend to expel huge clouds of smoke when started, as that oil burns off.
This is also true of automotive oil/air cooled engines, such as the flat four used in Volkswagen vehicles of the 1950's - 1980's, and the flat six in Porsche 911's until the wide temperature range of such engines ran up against tighter emissions controls. Those engines were also noted for their higher oil consumption.