Synthetic motor oils are blends of synthesized hydrocarbon fluids (SHF's) and esters derived from petrochemicals, and are manufactured by combining the various organic chemicals. Other synthetic hydrocarbon compounds are also suitable for lubricating oils, and manufacturers may blend two or more of these compounds together to achieve the desired properties. While they appear chemically similar to mineral oils refined from crude, they are pure chemicals that do not contain the impurities or waxes inherent in conventional mineral oils. Conventional mineral oils thicken or thin dramatically with changes in temperature. As a result, manufacturers add thickeners to conventional multigrade oils to slow thinning as engine temperatures rise. Synthetic oils have high resistance to changes in viscosity due to temperature, and thus have less of a requirement for thickeners. As such they provide a heavier, more stable protective oil film for engine bearings and piston rings than that provided by similar SAE-grade mineral oils.

Synthetic oil is superior to petroleum oil because it permits better cold weather performance and longer endurance. Synthesized compounds continue to flow at low temperatures. Synthetic 10W-30 oils flow at temperatures as low as -54°C (-65°F) and pump at lower temperatures than similar SAE viscosity conventional oils. Synthetic 15W-50 oils flow at -48°C (-55°F) and pump at temperatures as low as many conventional SAE 5W-30 oils. According to the San Antonio Air Logistics Center (SA-ALC), the primary benefit of synthetic oil is this superior performance at low temperatures.

Synthetics are also more thermally stable. Manufacturers claim that synthetic oils help improve fuel economy, reduce friction and wear, decrease oil consumption, better engine performance at lower temperatures and extend oil change intervals. However, since synthetic oil has improved fluidity, oil loss will occur more quickly through leaks because the thinner fluid will flow through a bad seal or worn ring. SA-ALC reports that the use of synthetic oils has not enabled them to reduce oil change intervals.

Although some synthetic compounds are not compatible with conventional oils adding a quart of synthetic oil to conventional oil produces a compatible mixture. However, the lower friction resulting from the use of synthetic lubricants makes them unsuitable for break-in.

The compliance benefits listed here are only meant to be used as a general guideline and are not meant to be strictly interpreted. Actual compliance benefits will vary depending on the factors involved, e.g. the amount of workload involved.

• Synthetic oil lasts two to five times longer than conventional oil thus waste oil generation can be reduced two to five times if synthetic oil is used.
• Synthetic oils have high resistance to changes in viscosity due to temperature. As a result they provide a heavier, more stable protective oil film for engine bearings and piston rings than is provided by similar SAE-grade mineral oils.
• Synthetic oil permits better cold weather performance and longer endurance.
• Manufacturers claim that synthetic oil yields better fuel economy, reductions in friction and wear, decreased oil consumption, improved performance, and extended drain intervals.

• Synthetic oil costs more than conventional oil. The higher cost is typically offset by reduced waste generation, however,
• Since synthetic oil has improved fluidity, oil loss will occur more quickly through leaks because the thinner fluid will flow through a bad seal or worn ring.
• Some synthetic compounds are not compatible with conventional oils.
• The lower friction resulting from the use of a synthetic lubricant makes them unsuitable for break-in.

Assumptions:

• 30 vehicles in fleet
• Labor Cost: $20/hr
• Labor: 0.5 hour per oil change
• Oil Disposal: oils are recycled at no cost to the facility
• Oil Cost: Synthetic - $14.51/gallon, Conventional - $4.42/gal
• Conventional Oil is changed three times per year, synthetic oil is changed once per year
• Filters cost $6.00 each
• Filter Disposal: Estimated at $100 per drum, 100 filter per drum
• Oil capacity of vehicle is an average of 12 quarts (or 3 gallons)