ARAI's unpublished study finds E20 fuel wears out rubber fuel-system parts in older E10 vehicles
One four-wheeler engine faced a valve issue during testing, though metallic parts and emissions stayed unaffected
A report by the Automotive Research Association of India, the body that had recommended rolling out E20 fuel in the first place, has now flagged a side effect that owners of older cars may want to pay attention to.
According to the study, running E20 petrol in vehicles built for the E10 standard leads to gradual deterioration of rubber components within the fuel system. Hoses, gaskets, seals and O-rings are named specifically, with the report suggesting these parts "may need replacement" once affected.
The study has not been released publicly, yet it has quietly shaped policy conversations. It has served as a reference point for both the government and vehicle manufacturers while assessing how compatible the country's ageing fleet really is with the higher ethanol blend.
How Engines Performed During Durability Testing
The engine durability portion of the study makes for interesting reading. Two four-wheeler manufacturers carried out tests, with sharply different outcomes. One OEM ran a BS-IV engine for 400 hours on E20 without a single durability concern, and performance was rated acceptable throughout.
The other told a different story. A thermomechanical failure of the exhaust valve turned up in an engine tested cumulatively for 809 hours, a term that essentially describes what happens when extreme heat combines with repeated mechanical movement, eventually causing a valve to warp, crack or fracture.
People familiar with the findings were quick to caution against pinning that failure squarely on E20, since such faults can stem from several engineering variables. It is also worth noting that engine durability tests typically run for around 2,000 hours, so the failure surfaced well before that benchmark was reached.
Two-wheelers fared better across the board. Three manufacturers tested their engines on E20 and reported no issues whatsoever, with acceptable performance throughout.
Emissions, Metal Parts And Mileage Under E20
Away from the rubber components, the news was largely reassuring. Across every vehicle tested, E20 showed no adverse impact on metallic parts, and tailpipe emissions stayed within the legislative limits set for E10-compatible vehicles. Evaporative emissions, too, remained within prescribed limits, and both startability and drivability were rated acceptable on the higher blend.
Fuel economy did take a modest hit. Consumption on E20 rose by two to six per cent compared with E10, though the extent varied from vehicle to vehicle. For everyday drivers, that translates into slightly more frequent visits to the pump, even as India continues to push ethanol blending as a long-term, cleaner alternative to conventional petrol.
With India having already reached the 20 per cent blending mark nationally, the debate over how well older, E10-designed cars can cope is unlikely to settle any time soon.
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