Anna University’s decision to revive a Tamil Nadu experiment in 100% ethanol vehicles brings an old transport question back into the national fuel debate: can a lower-carbon, domestically produced fuel reduce India’s dependence on imported crude without transferring the burden to vehicle owners, water-intensive agriculture and food security?
The university’s proposed research is rooted in work carried out at the College of Engineering, Guindy, between 1975 and 1985. Engineers modified petrol cars, two-wheelers and buses to operate on ethanol, tested the technology on a 2,000km route from Chennai to Ooty and Kanyakumari and demonstrated it to national and state leaders. The research showed that modified petrol engines could run on pure ethanol, but it also exposed the practical limits that continue to shape India’s ethanol policy: lower mileage, the need for engine changes and uncertainty over how fuel would be produced at scale.
That history matters because India’s current ethanol programme is no longer a laboratory exercise. The country’s ethanol-blended petrol policy has accelerated from blending below 1.5% in 2013–14 to a targeted 20% in 2025–26, according to the supplied report. The E20 programme requires fuel retailers to sell petrol containing 20% ethanol and 80% gasoline. The policy is intended to improve energy security, support farmers and distilleries, and reduce the environmental impact of petrol use.
But the shift also moves the debate from whether ethanol can burn in an engine to how the entire urban transport and agricultural system will absorb it. A fuel change affects vehicle design, mileage, refuelling systems, maintenance, household transport costs and the supply chains that produce the fuel. Anna University’s earlier work provides a useful technical baseline, but it does not by itself resolve these wider questions.
The 1970s experiment began after petrol prices rose from ₹4 to ₹6 a litre in 1973. The Tamil Nadu government asked professors at the Internal Combustion Engine Laboratory at Guindy to investigate alternatives. A team led by Professor T R Jagadeesan modified the carburettor, ignition system and cooling and heating systems of petrol engines so they could run on 100% ethanol.
The researchers found that ethanol had useful combustion properties. Jagadeesan told the Times of India that the fuel had a high flame speed and burned without producing black smoke. Its principal weakness was energy content: the heat produced by ethanol was about 60% of that produced by petrol, affecting mileage.
The road tests made that trade-off measurable. In a 1979 trial, one car recorded 7.2km per litre on ethanol compared with 11.46km per litre on petrol. On highways, the figures were 9.38km per litre and 14.9km per litre respectively. An Ambassador car tested in city conditions on January 21, 1980, delivered 6.2km per litre on ethanol against 9.54km per litre on petrol.
The team also showed that engine design could partly offset the performance penalty. It increased the compression ratio of a Fiat engine from 7:1 to 11:1 and modified its carburettor and other components. At the normal compression ratio, the ethanol engine achieved thermal efficiency of 26%, compared with 25% for petrol. With the higher compression ratio, efficiency rose to 32%.
Those results underline an important distinction in the present E20 debate. Ethanol blending is not the same as running a vehicle on pure ethanol. A vehicle designed and calibrated for a particular fuel blend may respond differently from an engine modified specifically for 100% ethanol. The older research therefore demonstrates technical feasibility, but it cannot be treated as proof that every existing vehicle will deliver the same performance with higher ethanol blends.
The Guindy team tested its modifications beyond the laboratory. Two cars completed a 2,000km journey from Chennai to Ooty, then Kanyakumari and back to Chennai. The route included hill roads, and the vehicles were restarted at Ooty without difficulty. The project also attracted the attention of Chief Minister M G Ramachandran, who wanted Ambassador cars at the state secretariat to run on ethanol. Vehicles used by senior officials were subsequently operated on ethanol and taken to the Anna University laboratory for refuelling.
The technology was demonstrated to Prime Minister Indira Gandhi and Finance Minister R Venkataraman. The team also tested ethanol in diesel applications, achieving an 80% ethanol blend in a diesel motor pump set and a 40% blend in a bus engine supplied by Ashok Leyland. Since ethanol and diesel do not blend easily, the fuels were supplied separately.
Yet the research did not progress into large-scale implementation. The central obstacle was not only engineering. Ethanol production at the time was closely tied to sugarcane, creating concern that agricultural resources used for fuel could be diverted from food. The same food-versus-fuel question remains relevant today, although the supply base has expanded.
India now produces ethanol from sources including sugarcane, maize and rice, while the university says newer production routes can also use agricultural residues. V Kumaresan, registrar-in-charge of Anna University, said the case for ethanol as an alternative transport fuel had strengthened because ethanol could be produced from several sources, potentially reducing pressure on food crops.
That potential depends on the scale and composition of the feedstock supply. Sugarcane and rice are water-intensive crops, according to the supplied report. A fuel policy that reduces crude-oil imports but increases pressure on water or food systems would not eliminate resource dependence; it would change its form. The available material does not establish how much of India’s future ethanol supply will come from agricultural residues, food crops or other sources, making the feedstock question a key area for the university’s research and for national policy.
The economic case for blending is equally mixed. India imports more than 80% of the crude oil it consumes, so domestically produced ethanol could reduce exposure to imported fuel and save foreign exchange. The policy also offers sugar mills, distilleries and farmers an assured buyer for surplus grain, sugarcane and maize. For cities, however, the relevant measure is not only the national fuel bill. Vehicle owners experience the policy through mileage, maintenance and compatibility with existing engines.
The supplied report notes concerns that higher ethanol content could lower fuel efficiency, accelerate corrosion and damage components not designed for the blend. These effects are especially important in a country where cars, two-wheelers, buses, agricultural engines and commercial fleets operate under very different conditions. A private car, a high-mileage motorcycle, a city bus and a farm pump set do not face the same fuel requirements or operating costs.
This is where Anna University’s proposed programme could add value. The university plans to study ethanol performance at different compression ratios, with an emphasis on flexible-fuel vehicles. The research will involve IIT Madras and universities in China and Brazil, and the Tamil Nadu government has provided a research grant of ₹5 lakh.
The institutional arrangement is significant because the ethanol question crosses administrative boundaries. Fuel policy is connected to national energy security, vehicle standards and oil marketing. Agricultural feedstocks involve farming and water use. Vehicle compatibility affects manufacturers, transport operators and consumers. Universities can test engine performance, but decisions on commercial deployment require coordination between these sectors.
The revival also shows how transport technology is shaped by timing. In the 1970s, the Guindy team had demonstrated that modified vehicles could run on pure ethanol and had recorded five years of testing without engine damage, according to Jagadeesan. But the fuel supply system and food-security concerns prevented the work from becoming a mass programme. Five decades later, the policy environment is more favourable because India has a national blending target and a broader set of possible feedstocks.
That does not make the old experiment a ready-made solution. The earlier mileage figures show that fuel substitution can impose a direct efficiency cost. The higher compression ratio improved thermal efficiency in a modified engine, but the supplied evidence does not establish how that result translates to today’s vehicle fleet, urban traffic conditions or E20-compatible models.
The larger urban question is whether India’s fuel transition can be designed around the full cost of mobility rather than only the composition of petrol. A successful programme would need to account for what drivers pay per kilometre, how buses and two-wheelers perform, whether components last, where ethanol is produced and how much water and agricultural land are required. The historic Tamil Nadu research makes these trade-offs visible because it recorded both the promise and the limitations of the fuel.
Anna University’s next phase will therefore be important less as a revival of a forgotten experiment than as a test of whether older engineering knowledge can be adapted to a different policy and vehicle environment. The confirmed direction is a research programme focused on compression ratios and flexible-fuel vehicles, supported by a ₹5 lakh state grant and collaboration with IIT Madras and universities in China and Brazil. What remains to be established is how the research will measure mileage, durability, feedstock sustainability and real-world operating costs as India’s ethanol blending programme expands.
