Jamie Whincup has revealed he has made "ergonomic" tweaks to his car for the first time in over a decade as he eyes a "comfortable" final full-time campaign.
Whincup and co-driver Craig Lowndes completed 131 laps during official pre-season testing at Queensland Raceway.
The 38-year-old, who will retire from full-time competition at the end of 2021, set the fifth-quickest time of the day, which was topped by Matt Stone Racing's Zane Goddard.
The new season will be Whincup's 16th with Triple Eight, having joined the team in 2006.
In that time, he has won a record seven drivers' titles and 122 races.
However, none of that has come comfortably; he suggested his age has caught up to him, triggering key changes in his car to help him feel more secure in the race seat.
"It's a big change, I haven't done it for a long time," he said.
"I did a few little race runs, I'm only talking 10 laps or so, but a few longer runs, just to make sure that we were suited to those ergonomic changes.
"It felt good, it felt positive. You can't keep doing the same thing year in, year out; you get stale and you get old.
"I'm trying to spice it up and keep it new.
"The body's pretty good, I had a good break, a good off-season, it's been three months since we got in the car.
"Any niggle you do have, now I'm a geriatric, any lower back or shoulder issue that may have come on last year... the three months off have certainly be able to recover that.
"I'm in a pretty good place to start the year."
Whincup completed a shakedown of his new car on Wednesday ahead of Friday's test.
While he didn't vault the #88 to the top of the time sheets, Whincup was satisfied with the day's running.
However, he admitted that his team has a long way to go on set-up ahead of the season-opener at Bathurst.
"Brand new car, which is exciting to start the year," he said.
"We had a little shakedown a few days ago, and today was a true test on feeling the car out, making sure it's comfortable.
"I've changed a few little things ergonomic-wise inside the car as well.
"It's been identical for 15 years, but this year, I decided to make a few little tweaks.
"I won't bore you with the detail, but yeah, getting used to those tweaks, but the car felt good.
"We spent most of the day just trying to go faster, trying to learn mechanically how to make the car quicker.
"Got a lot of data, but not sure if we made any gains forward, but we got a lot of information, so hopefully we can go through that and make some gains."
Whincup's 18th and final full-time Supercars campaign will commence at the Repco Mt Panorama 500.
Tickets for the event are on sale now.