Insufficient oil supply can be attributed to the following:

Re-fitting a turbocharger without adequate priming
Long periods of non-use
Broken or restricted oil feed pipe
Low engine oil pressure due to malfunctioning lubrication system
Low or no oil in sump
The use of sealants, which can restrict oil flow
Not priming a replacement oil filter with new oil. If this cannot be done then crank the engine with no fuel to establish oil pressure
Do not exceed idle conditions until oil pressure is established.

Effects of using silicone sealants                  Insufficient lubrication oil