An armada of tankers ferrying sanctioned oil around the globe is starting to get younger, bucking a months-long trend of using the world’s oldest and most dangerous vessels.Shortly after President Vladimir Putin’s invasion of Ukraine early last year, hundreds of aging tankers were snapped up by a cohort of faceless traders, intermediaries and investors to keep Russian oil flowing.

By some estimates, the purchases, which added to vessels that were already transporting crude for Venezuela and Iran, created a more than 900-strong dark fleet.Now, the average age of the ships being purchased is declining, according to data from VesselsValue Ltd., a researcher of shipping deals.

Two industry executives said that clampdowns in Asia were likely catalysts for the shift, following a spate of detentions in recent months over safety issues.China, one of the top consumers of Russian and Iranian oil, recently ramped up checks on older tankers at the key port of Qingdao, forcing some to wait more than a month to unload their cargo.

Anxiety over aging ships was heightened when a 26-year old vessel exploded off Malaysia in May.Singapore has also detained tankers for failing safety inspections at a record clip in recent months.

Newer vessels, provided they are well maintained, should help to allay fears by some importers over their seaworthiness, though the fleet remains awash with vintage ships.

“Safety concerns surrounding older vessels is one of the reasons that buyers are opting for newer vessels,” said Rebecca Galanopoulos Jones, a senior analyst at VesselsValue.The average age of tankers being sold to undisclosed buyers — one defining characteristic of a ship being part of the dark fleet — fell to 15 years this month, according to VesselsValue.

As recently as October, it was 19 years.Demolition delayThe specifics of dark fleet tankers vary.

Often, though, they are older vessels without industry-standard insurance or other western services, and owners that are tough to trace.

Ships are near or over 20, an age at which vessels would typically be scrapped.

Certain countries take a hard view on older ships.

In addition to the Chinese checks, India moved to ban vessels older than 25 years of age from entering its ports earlier this year.

“Some shipowners are getting more comfortable with handling restricted crude such as Russian flows, as they see that this trade is here to stay,” said Anoop Singh, global head of shipping research at Oil Brokerage Ltd.

“They’re now more willing to invest in younger ships that’ll meet wider industry standards for longer.”When buying for the Russia trade first emerged, it made sense to purchase the oldest vessels available.

Those ships are the cheapest, and operating without western services enabled them to bypass many of the sanctions in place on oil exports, including a $60-a-barrel price cap on Russian crude that was imposed by the Group of Seven.The surge in demand for ships has extended the lifespan for many.

Not a single large crude tanker has been scrapped for seven months, something that hasn’t happened since at least the mid-1970s, according to Clarkson Research Services Ltd., a unit of the world’s largest shipbroker.Tankers are also spending more time in transit.

The pool of buyers for Russian crude has shrunk since the war, meaning cargoes that used to be hauled just a couple of days along the Baltic Sea now travel for weeks to get to China and India.

That’s pushed benchmark oil tanker earnings to around $100,000 a day on two occasions since the war broke out, compared with an average of $23,000 a day since 2017.

Further purchases of younger ships boost the chances of rates returning to the higher level as it trims the supply of ships for conventional trades.There is a strong safety rationale for the move to newer vessels.

In May, an aging tanker was found to have more than 20 defects during an inspection in China.

And a lot of the older tankers that can serve the trade have also already been acquired.“The pot of old bangers is running dry so it’s a natural progression that newer ships will be taken,” said Halvor Ellefsen, a tanker broker at Fearnleys Shipbrokers UK Ltd.

“If it continues, it will mean a tighter regular tanker market, but also a more certain supply of oil from sanctioned countries.”