[A26B]

Some symptoms & sources of momentary exhaust oil smoke, without excessive oil consumption.

1. PCV System. Most always affects L exhaust only:
Accumulation of oil in plenum from PCV system. Oil enters plenum through PCV vacuum source on L side of plenum behind T-body. Oil gravity flows to rear of plenum and enters mostly into #7 cylinder. Exam of #7 plug may show light oil coloration.
Not a cause for concern and has very little effect on engine performance.

Solution: Install Oil "Catch Can" system.


2. Injector Housing/Cyl Head Gasket. Can affect L and/or R exhaust.
Infrequent occurrence but known as potential source of oil smoke in exhaust. Most often occurs in high mileage engines.
Over time, injector housing bolts become loose, reducing clamping force on gasket. Differential pressure between intake vacuum and crankcase vent port causes gasket to migrate towards intake runner & communicate. Considering the injector housings have isolated passages for 3 different functions, (i) intake runners w/vacuum), (ii) crankcase ventilation and (iii) coolant @16psig, the need for absolute gasket sealing is essential.
Communication between intake runners & crankcase ventilation passages will result in oil laden vapor contamination, i.e. burning oil.

Solution: Replace Injector Housing Gaskets

3. Exhaust Valve Stem Seals. Can affect L and/or R exhaust.
Only the 1990 model LT5 engines did NOT have exhaust stem seals. All other models, 91~95 have both exhaust & intake valve stem seals.
Typically, any noticeable oil smoke in the exhaust, only occurs at startup or after extended idle and is not normally detrimental to engine performance.

Solution: Install Valve Stem Seals on Exhaust Valves. NOTE: This is not doable without significant cost to R&R cylinder heads to install seals. Not recommended or necessary for engine performance unless engine is very high mileage or damaged otherwise.