E20 can damage rubber parts in older cars, says ARAI report that wasn't made public

The government's aggressive push to expand the use of E20 fuel (petrol blended with 20% ethanol) might come with some cost for millions of older vehicles. A study by the Automotive Research Association of India (ARAI) found that using E20 in E10-compatible vehicles could lead to deterioration of rubber fuel-system components such as hoses, gaskets, seals and O-rings, with some parts potentially requiring replacement, according to the summary of the report, which was not made public.

Two four-wheeler manufacturers carried out the "engine durability" test as part of the study, according to a report in The Times of India. While one manufacturer found no problems after 400 hours of testing, in the other case, "thermomechanical failure of exhaust valve was observed in the engine(s) tested cumulatively for 809 hours", the newspaper reported. The ARAI study, however, found no adverse impact from E20 on metallic components.

The findings assume significance as the Centre continues to promote higher ethanol blending as a key strategy to reduce dependence on imported crude oil, cut emissions and support farmers. However, the transition is taking place even though a large majority of vehicles on Indian roads — estimated at over 80% — are not compatible with E20 fuel. Most vehicles, particularly those manufactured before 2023, were designed primarily for E10 or lower ethanol blends.

People have complained of a drop in mileage and wear and tear due to the use of E20 fuel in E10-compatible vehicles. The government has rubbished the claims.

Auto enthusiast and rally driver Ratan Dhillon from Team Bharat told India Today Digital that there was evidence that could link the wear and tear in cars to E20 petrol. "There is wear and tear from ethanol, and we will prove in court. Fuel filter and the entire pipeline gets choked," he said on July 5 during the first offline protest at New Delhi's Jantar Mantar against the implementation of the ethanol-blending programme.

That the government should make public all research documents related to the ethanol-blending programme, has been among the demands of the protesters agitating under the banner of Team Bharat.

The ARAI study, which began in March 2022, examined the impact of E20 on E10-compatible vehicles. The ARAI study, which was not made public, found that the overall impact of E20 on E10-compatible vehicles was mixed.

ARAI STUDY'S FINDINGS ON E20 USAGE IN E10–COMPATIBLE VEHICLES

The summary of the report stated that vehicle tailpipe emissions and evaporative emissions remained within the prescribed legislative limits, while durability performance was generally comparable to that of E10 fuel. However, the study noted an increase in emissions in a few vehicles after mileage accumulation on E20. It also found that fuel consumption increased slightly — by around 2% to 6% compared with when E10 was used — although the exact increase varied across vehicles.

Startability and drivability were found to be satisfactory with E20 in most cases, except for BS-IV two-wheelers, where an exception was noted, according to the ARAI report.

On engine durability, the tests involved multiple manufacturers, the report stated.

For four-wheelers, two Original Equipment Manufacturers (OEMs) conducted evaluations.

One BS-IV engine showed acceptable performance with E20 after 400 hours of testing. However, issues arose with a BS-VI turbocharged engine after 265 hours, reported The Times of India.

In another set of tests totalling around 809 hours cumulatively, a thermomechanical failure of the exhaust valve was observed in one case. Some experts suggested there could be other reasons behind the failure, while others noted that standard durability tests often run for up to 2,000 hours, according to The Times of India report.

For two-wheelers, tests by three manufacturers found no major issues, with performance deemed acceptable.

NO ADVERSE EFFECT ON METAL PARTS, BUT RUBBER PARTS COULD NEED REPLACEMENT

Importantly, the ARAI study found no adverse impact from E20 on metallic components or the vehicle overall in the tested vehicles.

As per the ARAI document, the Society of Indian Automobile Manufacturers (SIAM) has also pointed out that rubber parts in fuel systems — hoses, gaskets/seals, and O-rings — might show deterioration and could require replacement when using E20.

This comes against the backdrop of the government's accelerating ethanol programme. Production of E20 material-compliant vehicles began in 2023, and from April 2025, all new vehicles are required to be both E20 material and fuel compliant. Earlier vehicles, including many E10 models produced since around 2010, form the bulk of the fleet.

In May, the government tasked ARAI with a further study on E25 (25% ethanol) impacts on existing E10 and E20 vehicles, focussing on mileage, engine condition, emissions, and costs. This reflects ongoing efforts to assess higher blends amid surplus ethanol availability.

The rollout of E20 has been positioned as beneficial for reducing oil imports and promoting cleaner fuel. However, concerns persist among owners of older vehicles regarding long-term effects on components like carburettor filters and rubber elements, which vehicle owners highlighted at a recent protest at Jantar Mantar.

The ARAI findings underscore the need for vehicle owners with pre-2023 models to monitor fuel system components closely.

Union Minister Nitin Gadkari has been a champion of the E20 fuel, pushing for increased blending targets.

While the government and industry maintain that E20 is safe overall based on extensive testing, the report's details on rubber deterioration and specific engine test observations have added nuance to the discussion.