Australia's Daniel Ricciardo posted the third fastest time overall on day four of Formula One testing in Spain.
But it was his new Renault teammate Nico Hulkenberg who ended the day on a high on Thursday, clocking the fastest lap so far by any of the new crop of cars.
Ricciardo, who quit Red Bull to join Renault after last season, lapped in one minute 17.785 seconds - his team's first sub-1m 18s time of the week - on the softest and safest tyres on a cold, but sunny Thursday morning at Barcelona's Circuit de Catalunya.
And 31-year-old German Hulkenberg, who holds the unwanted record of most races (156) without once stepping on the podium, crossed in 1:17.393 in the late afternoon session.
Renault, who had said before testing that their engine had made a big step up over the winter, did less mileage than their rival teams, however.
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"I'm feeling more and more comfortable each time I step into the car," said Ricciardo on Renault's official Twitter site.
"We didn't put in as many laps as we planned but that's testing and we were caught up with some smaller issues which meant we were stuck inside the garage.
"The timing looks good on paper but it is impossible to be sure of the respective plans to put our lap times in perspective."
Toro Rosso's Thai rookie Alexander Albon was second fastest having led the lunchtime timesheets with a lap of 1:17.637 while champions Mercedes unlocked a little more pace and went faster than Ferrari.
The relative pace of the two frontrunning teams from 2018 remained unclear, with Mercedes' Valtteri Bottas suggesting the Italians were a step ahead while Ferrari's Charles Leclerc accused the champions of "sandbagging".
British-born Albon, one of three F2 graduates making their F1 race debuts when the season starts with the Australian GP in Melbourne on March 17, completed a whopping 136 laps - on top of 132 on Tuesday.
Britain's five-times world champion Lewis Hamilton was fifth, just behind Bottas who set his best lap on the softest and fastest tyres, but did his stint in the colder morning temperatures.
Ferrari's Leclerc was sixth on harder tyres than any of those above him.
Alfa Romeo's Italian Antonio Giovinazzi did the most laps of all on Thursday (154), but also twice brought out the red flags, while British rookie George Russell managed the fewest (17) in the Williams.
Poland's Robert Kubica was also on track for Williams, who only started testing on Wednesday afternoon, and did 48 laps.
