Gasoline and diesel sales over May 1-15 fell by about 20%, while jet fuel consumption slumped by nearly 38%, versus April 1-15 levels, the data compiled by the state refiners showed.
"Trucking activity is almost half of what it used to be in normal times," SP Singh, a senior fellow at Indian Foundation of Transport Research & Training, said.
"Most of the business that they were getting from small and medium business has been hit due to lockdowns," Singh said, adding only a fraction of 5.5 million trucks is currently running on roads due to lockdowns.
Indian fuel demand had recovered to near pre-COVID levels in March but has been declining since April was given restrictions amid a staggering spike in infections to record highs.
India on Monday reported 281,386 new coronavirus infections over the last 24 hours, while deaths rose by 4,106. The South Asian nation's total caseload is 24.97 million with the death toll at 274,390, health ministry data showed.
Federal health officials have warned against any complacency over a "plateauing" in the rise of infections and urged states to strengthen their medical infrastructure and workforce.
India's demand for transportation fuels is expected to witness a sharper slump in May due to more impending restrictions, analysts say.
Due to a decline in local fuel sales, Indian refiners have started cutting crude processing and import State companies - Indian Oil Corp, Hindustan Petroleum Corp, and Bharat Petroleum Corp Ltd - own about 90% of India's retail fuel outlets.
Domestic fuel sales by state retailers over May 1-15, however, were higher versus a year earlier when there was a nationwide lockdown.