Few applications place more stress on lubricants than taxi cabs, particularly those operating in the desert heat of Las Vegas, NV. The combination of excessive idling, stop-and-go driving and high ambient temperatures creates the ideal scenario for lubricant failure, resulting in sludge formation and catastrophic component failure.

Fleet vehicles, heavy-duty pickups, work trucks and other commercial applications operate under severe service. In addition, drain intervals are getting longer. For engines and transmissions to last as designed and achieve maximum performance, lubricants today must protect against elevated heat and its associated problems for longer periods of service.

In conducting this field study, AMSOIL sought a test partner with vehicles used in the most demanding conditions possible. A Las Vegas taxi company was selected due to the challenges inherent to taxi applications and the extreme desert heat, which presented a worst-case scenario that further challenged the lubricants. In fact, the taxi company had been experiencing rampant engine failure using synthetic blend motor oil recommended for API SN/ILSAC GF-5 service requirements and changed every 5,000 miles. Engine failures occurred predominantly during hot summer months due to excess sludge clogging the oil pickup tubes and starving the engines of oil. The severity of service also required frequent transmission fluid changes every 20,000 miles.

AMSOIL Signature Series Synthetic Automatic Transmission Fluid and Signature Series Synthetic Motor Oil were installed in six of the fleet’s vehicles. The test vehicles were placed into service for approximately 18 months, during which they were operated within the fleet’s service area of Las Vegas up to 24 consecutive hours each day, with the engines often shut down only during refueling or personnel changes. Excessive time idling combined with stop-and-go driving loaded with passengers and cargo characterized typical driving conditions. During summer months, ambient temperatures often exceeded 100ºF, further increasing severity.

Motor oil in the test vehicles was scheduled to be changed at a minimum of 900-hour intervals. The actual oil change intervals of the vehicle reported in this study were 1,005 hours (approximately 15,000 miles). Transmission fluid wasnot changed in any of the vehicles.

Field testing proves that AMSOIL Signature Series Multi-Vehicle Synthetic ATF and AMSOIL Signature Series Synthetic Motor Oil provide superior protection against sludge and wear for extended drain intervals in severe service. Components from a Las Vegas cab’s transmission revealed minimal distress despite accumulating 7,033 hours (102,582 miles) of severe service on a single fluid change. Engine parts demonstrated similar results, with the cylinder heads, oil pan and front cover clean and virtually free of sludge.

The performance of each fluid in notoriously severe applications operating in challenging conditions indicates their capability to protect in the harshest environments faced by fleet vehicles, heavy-duty pickups, work trucks and personal passenger cars. Results confirm the fluids’ ability to provide reserve protection beyond the severe-service recommendations of original equipment manufacturers (OEM’s).

Read or download the Las Vegas Taxi Cab Field Study