Oil percentage in glowplug engines and diesel engines are difference.

Let us see at the operating instruction for the Enya engine:

Enya 06 Main bearing: Light alloy Oil percent: 20%
Enya 06D Main bearing: Light alloy Oil percent: 25%

Enya 15-II Main bearing: Bronze Oil percent: 20%
Enya 15D-II Main bearing: one ball bearing and Bronze Oil percent: 25%

Enya 41-4C R/C Diesel Main bearing: all ball bearing Oil percent: 25%

The diesel engine need more oil than glowplug engine. The 4 stroke diesel engine need more oil to give enough oil to lubricate moving parts in crankcase.

And other engine as PAW to example are oil percent difference between engine with plain bearing and engine with ball bearing:

25% for engines with plain bearing.
20% for engines with ball bearing.
The lowest are 15% for ball bearing if the engine are used as racing engine with high kerosene in fuel.

The racing diesel engine who are running at 15% oil can not last long as a normal operated diesel engine.

In generally the diesel engine need more oil due low fuel consumption and enough oil film against hi load at bearing.