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Engine Oil Specifications

 

Current Recommendations

KJ Engine (2.3L)

KL Engine (2.5L)

Notes: Where Group III synthetic is specified, Group IV or Group V based oil that meets or exceeds Group III specs may be used.

 

Synthetic Oil Change Interval Recommendations

Schedule 1 conditions - every 10,000 miles or 16,000 kilometers*

Schedule 2 conditions - every 7,500 miles or 12,000 kilometers

* Use of a high-quality oil filter designed for extended oil change intervals is recommended

 

Conventional Oil Change Interval Recommendations

Schedule 1 conditions - every 7,500 miles or 12,000 kilometers

Schedule 2 conditions - every 5,000 miles or 8,000 kilometers

 

Oil Change Interval Schedules

Under typical driving conditions, follow Schedule 2.  If none of the following apply, follow Schedule 1.

 

Make-up Oil

As engines age, bottom end wear allows increased amounts of oil blow-by to occur in the combustion chambers causing a gradual increase in oil consumption.

While a newer engine can consume as little as one-fourth of a US quart (or liter) between oil change intervals or less, a well worn engine may consume as much as 5-10 times that amount or more before cylinder compression levels fall below specification.  These engines will require the addition of make-up oil between oil change intervals to prevent the oil level falling below 'L' on the dipstick.  The difference between 'L' and 'F' on the dipstick equates to approximately one US quart or one liter.

 

Choosing an Oil Viscosity

Q: What is the difference between a "w30" (e.g. 5w30, 10w30) and "w40" (e.g. 5w40, 10w40) engine oil?

A: This specifies the viscosity of the engine oil when hot (at 100C).  Compared to a w30 oil, a w40 oil may offer improved protection when the engine is subjected to sustained extreme heat/load conditions and/or may also help reduce oil consumption and improve oil pressure on well worn engines.

Q: What is the difference between a "5w" (e.g. 5w30, 5w40) and "10w" (e.g. 10w30, 10w40) engine oil?

A: This specifies the viscosity of the engine oil when cold (at 0C).  Compared to a 10w oil, a 5w oil flows with less resistance when the engine is cold started, which improves engine wear protection at cold start and reduces starter and electrical system load in very cold temperatures.

Q: Why is a synthetic 5w30 oil recommended for year-round use but a conventional 5w30 oil only acceptable in cold temperatures?

A: Synthetic engine oil has superior shear stability and thermal stability compared to a conventional multi-grade engine oil with the same viscosity.  Shear stability refers to how well a multi-grade oil maintains its rated viscosity at operating temperature while in service while thermal viscosity refers to an oil's ability to resist breakdown under brief periods of high-heat stress.  Conventional multi-grade oil is achieved by adding viscosity enhancing additives (VEAs) to a single-grade base oil.  In the case of conventional multi-grade 5w30, VEAs are added to a 5w base oil until a w30 viscosity is achieved when hot.  For a conventional 10w30 oil, VEAs are added to a 10w base oil until a w30 viscosity is achieved when hot.  While both 5w30 and 10w30 have the same viscosity at engine operating temperatures, 5w30 uses a thinner base oil and more VEAs while 10w30 uses a thicker base oil and less VEAs.  Because VEAs tend to break down under shear stresses and high heat, 5w30 is less "durable" and only acceptable for use in very cold climates to aid cold starts.  In the case of synthetics, the very high VI of synthetic base oil means that a 5w30 synthetic achieves its multi-viscosity properties without VEAs.  As a result, using a synthetic 5w30 year round (or even a 0w30) is no problem.

Q: What oil viscosity is best for the KJ (Miller Cycle) and KL (2.5L DOHC V6) engine?

A: If using a conventional or synthetic blend oil, 10w30 should be used.  When using fully synthetic oil, a 5w30 or 0w30 should be used (as synthetic 10w30 is relatively rare).  Also, when using synthetic oil, a w40 oil can be used in place of a w30 oil if desired.  In the case of the KL engine, a synthetic blend 10w40 may be used.

Q: What oil change schedule should I follow?

A: Oil change schedules will vary depending on local climate, driving conditions, and driving habits.  The only way to know for certain if engine oil is being changed often enough (or too often) is to have an oil analysis and TBN test performed by a lab on a used sample of oil taken at the end of an oil change interval.  Companies like Blackstone Labs provide free testing kits and a standard analysis costs less than $25.  Generally, Schedule 2 should be followed under typical driving conditions.

 

Current API Base Stock Categories

Group I - Crude mineral oil is refined using solvents.  The process of refining crude oil with solvents was commercially perfected in the 1930s with the advent of recyclable solvents.  As techniques improved, the quality of the base oil produced did as well.  By the 1950s, base oil performance characteristics stayed relatively steady, with minor improvements in motor oils during this period coming mostly from advances in additive packages until modern forms of hydroprocessing were developed and commercialized in the 1970s.  Group I base oil generally has a VI (Viscosity Index) of 80-119.

Group II - Crude mineral oil is refined using a modern hydroisomerization process developed in the 1980s and licensed by Chevron under the name ISODEWAXING.  Commercial production was first established in 1994 and the process produces a base oil with a viscosity index similar to that of Group I (80-119+) but with much improved performance characteristics and far fewer impurities.  A subcategory, Group II+, is essentially Group II base oil with a VI between 110-119.  Passenger car motor oils, originally 100% Group I, began producing Group I/II blends to improve performance and meet newer API specifications in the mid 1990s.  Current conventional passenger car motor oils (PCMOs) are now almost entirely Group II if not 100%.

Group III - Crude mineral oil is refined using an extended or higher "severity" version of the three-way hydroisomerization process used for Group II oil to achieve a very high VI.  Group III oils are marketed as "synthetic" in North America because second-generation Group III has performance characteristics and VI (120+) similar to that of traditional Group IV.  In the industry, Group III base oils are sometimes referred to as unconventional base oils (UCBOs) or very high viscosity index (VHVI) base oils.  A subcategory, Group III+, is essentially a Group III base oil with a VI of 135 or higher and often used in very wide viscosity spread applications, such as 0w40 and 5w40 motor oils .  Group III+ is typically produced using modern, very high severity hydroisomerization on slack wax, which has a very high VI, or wax produced through a GTL (gas-to-liquid) process used by Mobil and Shell.

Group IV - Traditional "synthetic hydrocarbon" base oil comprised of commercially synthesized hydrogenated polyalphaolefins (PAOs) and marketed for use in passenger cars since the 1970s are now classified as Group IV. Historically, synthetic hydrocarbons have had superior performance characteristics not achievable with Group I base oils.  However, by the end of 1999, the performance characteristics of second generation Group III base oils effectively matched that of PAOs in most commercially significant finished lube applications with one notable exception being a relatively niche market of arctic motor oils.

Group V - A catch-all group for any synthetic and mineral base oils not included in Groups I through IV such as esters, silahydrocarbons, chlorotrifluoroethylene (CTFEs) polymers, perfluorinated (PFPAE) fluids, et cetera.

References: Some API base stock descriptions paraphrased from Modern Tribology Handbook, Vol I, edited by Bharat Bhushan, 2001 CRC Press LLC

 

Original Recommendations (1993-2002)

KJ, KL:  API Service SG/SH/SJ/SL, ILSAC GF-I/GF-II/GF-III conventional engine oil