Oil rose towards $84 a barrel on Tuesday amid speculation that a tight global fuel market could get even tighter this winter.
Benchmark Brent crude futures edged up 0.2 percent to $83.80 a barrel in European trade, after having reached $84.60 on Monday, the highest since October 2018.
West Texas Intermediate futures were up 0.2 percent at $80.66 a barrel after climbing 1.5 percent the previous day in the run-up to the Northern Hemisphere winter.
Citigroup Inc. said oil prices may hit $90 a barrel at times this winter as gas-to-oil switching drives stockpiles lower.
Power prices have risen to records in recent weeks as a rebound in global demand contributed to energy shortages in Asia, Europe and the United States. The energy crisis affecting China is expected to last through to the end of the year.
The supply side remains tight as the Organization of the Petroleum Exporting Countries and allied producers, or OPEC+, is sticking to plans to gradually bring back output, rather than quickly boost supply.