The crew of Pamela Relph, Grace Clough, Dan Brown, James Fox and cox Oliver James powered away from the start.
They finished in a new world best time of three minutes 13.76 seconds, over 15 seconds clear of second-placed Italy.
There was also a bronze for Tom Aggar in the mens singles sculls event as he finished behind Australian Erik Horrie and Russian Alexey Chuvashev.
Aggar's time was 4:49.75 with Horrie winning in 4:41.74 and Chuvashev clocking 4:47.97.
The four were delighted to maintain the boat's unbeaten record, which goes back to the 2011 World Championships
"We knew we were on for a good time as we've had a good training camp and a great block of training," said Relph, who won gold at London 2012.
"We wanted to challenge ourselves here in the heat and with conditions the way they were today we knew it was on to break the record again today."
Former cyclist Rachel Morris finished fourth in the women's single sculls final behind Israel, Norway and Brazil as she recovers from shoulder surgery.
Great Britain's mixed coxed four continued their dominance with gold at the Para-Rowing World Cup in Italy.