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With the current use of bio-renewable fuel, the application of Ethanol in Flex-Fuel vehicles presents a very low CO2 emission alternative when the complete cycle, from plantation, fuel production, till vehicle use, is considered. In Brazil more than 80% of the car production is composed of Flex-Fuel vehicles. Due to the lower heating content of the Ethanol, more aggressive combustion calibrations are used to obtain the same engine power than when burning gasoline. Such Ethanol demands, associated with the continuous increase of engine specific power has lead to thermo-mechanical loads which challenges the tribology of piston rings. The ethanol use brings also some specific tribological differences not very well understood like fuel dilution in the lube oil, especially on cold start, corrosive environment etc. Under specific driving conditions, incipient failures like spalling on nitrided steel top rings have been observed.

An innovative two-piece oil control ring design, named Monoland, has been developed aiming to have high conformability and optimized specific contact pressure. As a result, the Monoland provides superior oil scraping efficiency with reduced friction losses. These were achieved by tailoring the geometrical features and material properties. A solution for oil control rings of minor moment of inertia and higher conformability was achieved through a new geometrical design concept where: a) only one land of the ring is in contact with the bore, b) the outer and inner faces are linked by two convergent planes and by means of a Powder Metallurgy (P/M) steel that was tailored to a lower modulus of elasticity. The new ring design had its structural robustness checked by finite element analysis and its scraping capacity measured by lubricant oil consumption measurement in engine tests.