SCG Classic Car Troubleshooting Checklist - Excessive Oil Consumption

Internal Engine Components - Bottom End

1. Pistons are improperly fitted (clearance too wide)\
2. Piston finish incorrect (highly unlikely today)
3. Ring grooves too wide
4. Oil drain holes in ring grooves clogged
5. Broken ring
6. Rings installed incorrectly (many variations here)
7. Bad ring seating in cylinder wall
8. Ring gap clearance too small
9. Piston/rod out of alignment
10. Scored rod bearings
11. Crankshaft throws badly worn
12. Oil seals badly worn
13. Tapered or out-of-round cylinder walls
14. Heat-distorted cylinder walls
15. Block out of alignment with crankshaft

"Plumbing" Defects

1. Oil level too high
2. Clogged breather or PCV
3. Blow-by pressures high
4. Oil return passages clogged
5. Poor grade of oil
6. Oil diluted with gas
7. Oil saturated with particles from combustion (oil change overdue)
8. Excessively high oil pressure

Internal Engine Components - Top End

1. Worn valve guides
2. Intake valve guides installed incorrectly
3. Valve stem oil seals worn, hardened or not installed

Other Possible Causes

1. PCV causing vacuum problem
2. Fuel mixture too lean
3. Cooling system cavitation causing localized overheating
4. Late ignition timing