level off at coolant temperatures of 60°C (140°F) and above. For fuels with higher sulfur content up to · 1000 ppm, wear rates lev

level off at coolant temperatures of 60°C (140°F) and above. For fuels with higher sulfur content up to 1000 ppm, wear rates level off at higher operating temperatures of 80-100°C (176-212°F).55 In the almost twenty years since these findings were published, sulfur has been all but eliminated from fuels in North America and Europe. Automakers now use advanced thermal management to allow rapid engine warmup, that when coupled with reduced sulfur fuels, neutralize the low temperature acid formation. Reducing sulfur content helps engines run cleaner and improve the efficiency of emissions control devices. Since the 1990s, the EPA has been working towards cleaning up fuels and reducing sulfur content. The EPA finalized their Tier 2 standards for sulfur content of domestic fuels in 2000 which reduced its content by some 90%. Tier 3 standards in effect since 2017 limit sulfur content to 10 ppm, providing the market what is considered “ultra-low sulfur fuels.” In most markets, these fuels are also enriched with ethanol, typically not to exceed 10%. The prevalence of ethanol enriched fuels also raises the concern that it too can cause damage to Al-Si engines, however limited research would indicate that the presence of ethanol does not significantly affect the formation and function on tribofilms required to support the Al-Si cylinder system.56 Taking into consideration engines operated since new in 2017 with ultra-low sulfur fuels in cold climates have benefitted from reduced acid formation, engines built and operated prior to the implementation of the Tier 3 standards would be expected to have experienced higher wear in cold climates proportional to the sulfur content of the fuel available at that time. Although the coolant thermostat helps to bring the engine up to proper operating temperature, oil and coolant temperature will take longer to normalize, even when the engine is fitted with a modern laminar flow oil to water heat exchanger. The result could be an engine that reaches the desired coolant temperature however the oil may still be in the danger zone for acid formation. This is particularly of concern for vehicles driven short distances, even in warmer climates, as combustion byproducts combine with moisture in the crankcase to form acids that can damage both the piston rings and cylinder bores. In instances where the oil does not reach full operating temperature regularly, like in stop and go traffic in cold weather, Porsche advises changing the motor oil more frequently in these instances to ensure the engine oil is 100% effective in protecting all internal engine components.57 Some auto manufacturers recommend that vehicles driven in cold climates may benefit from a short 10-30 second warmup58 to allow all areas of the engine and transmission to be properly lubricated above -18°C (0°F) but below 0°C (32°F), however above freezing temperatures, modern engines do not need to be warmed up.59 Besides causing excess emissions and wasting fuel, extended periods of idling under cold start introduces extra fuel into the cylinder bores that can wash the lubrication off the cylinder walls. Manufacturers recommend driving at moderate speeds for a short distance to allow the engine to come up 55 MMC All Aluminum Cylinder Block for High Power SI Engines. Toshihiro Takami, et al. Toyota Motor Corp & Toyota Central Research and Development Labs, Inc. SAE Technical Paper Series 2000-01-1231. 56 Sliding wear behavior of eutectic Al-Si alloy under lubricated conditions: An investigation on the effect of ethanol (E85) addition. Victor Vimalrajan Francis. University of Windsor. 57 2007 Porsche Cayman S Owners Manual. Maintenance, Car Care. Pg. 210. 58 Summary of OEM Idling Recommendations from Vehicle Owner’s Manuals. Blackmon, et al. ORNL/TM-2016/50. Oak Ridge National Laboratory. 59 http://idlefreevt.org/how-long-a-vehicle-should-warm-up.html LN Engineering Technical Library. Copyright ©2019 LN Engineering LLC