General Recommendations

Pretty much any modern oil API Starburst or SJ, SL, or SM rating will work fine in unmodified automotive gasoline engines.  Although your engine may have called for an API MM, MS, SB, SC, SD, SE oil, you can use the latest SM oil because the ratings are backwards compatible.  Potentially, SM Starburst oils may not have enough ZDDP for aggressive aftermarket valve trains.  CI-4+/SL oils would likely have all of the ZDDP required for demanding flat tappet cam applications.  In either case, the important thing is to use an oil with the same hot-viscosity rating as recommended by the manufacturer.  That is, if your owner's manual called for a SAE 30 or a SAE 10W-30 oil, you can also safely use a 0W-30 or 5W-30.  You will not get better protection with a higher viscosity oil like a 10W-40 or a 20W-50 unless your engine oil temperature is hot enough to reduce the heavier oil's viscosity to that of a 30-weight oil at normal engine oil temperatures (9.3 cSt to 12.5 cSt).

Wear is minimized in automotive engines when the engine oil viscosity is within its design range.  An engine will wear faster when the oil is too thin or too thick so viscosity must therefore be in the right range for maximum engine life.  Excessive viscosity also unnecessarily stresses oil pumps.  Although most ACCCC members do not drive their collector vehicles in the winter, the low temperature flow capability of a 0W or 5W oil allows it to flow to the bearings faster than heavier weight oils at start-up.  Using an excessively heavy oil will cause the safety relief valve to bypass oil back to sump at cold start-ups, thereby reducing oil flow to the bearings.  Winter-driven daily driver vehicles would definitely benefit from low viscosity 0W/5W oils.

We do not recommend the use of racing oils (oils with high levels of ZDDP) in street-driven vehicles due to their generally lower levels of detergency.  However, engines with highly stressed valve trains may benefit from racing oils if short OCIs are used to minimize sludge formation.  However, HDEOs often contain the same or greater amounts of ZDDP but with much better detergents at a lower cost.  Compare Valvoline VR1 vs PetroCanada Duron XL for more information. Esso also recommends the use of HDEOs for flat tappet engines (see Esso's Flat Tappet Engine Wear Bulletin for more information).

Engine cleanliness has always been of great importance for a well-maintained car.  Sludge became a major problem during the winter of 1935 and road-draught crankcase ventilation systems were introduced as a result.  By 1962, Positive Crankcase Ventilation (PCV) systems were introduced for emissions and improved sludge control.  You can help minimize engine contaminants with a few simple things:

• Ensure the crankcase ventilation system in good working order.
• Ensure that the crankcase ventilation filter is clean and in good condition.  For road-draught and open PCV systems, consider using a high efficiency filter in place of the standard oil filler cap filter while driving to minimize the amount of dust from entering the crankcase.
• Ensure that the manifold heat control system is in good working order.  This allows faster warm-ups and minimizes any liquid fuel from entering the crankcase.  Remember: it is actually the intake manifold that is warmed-up when your engine is warmed-up (ie, running smoothly with the choke off).
• Drive the car regularly long enough to allow the engine oil to reach operating temperature.  This helps to drive off condensation and minimizes fuel dilution.
• Use a good quality paper element air filter cartridge if so equipped.  Low restriction filters generally do not filter as well as OEM-style filters.