Jamie Whincup has admitted taking his foot off the pedal during last year's Supercars Enduro Cup but is adamant there will be no repeat in 2016.

The endurance season begins on Sunday with the Sandown 500 in Melbourne, where stakes are as high as they come in V8 racing.

After competing for 75 points in each race since March, 300 points are on the line in the 500-kilometre classic.

Whincup, who holds a 131-point championship lead over teammate Shane van Gisbergen, knows he can't afford another performance like last year.

Entering the endurance season well off the title pace, Whincup and co-driver Paul Dumbrell won pole but slumped to 15th after a pit-lane puncture.

It didn't get much better for the Red Bull Commodore, with 18th place at Bathurst and a poor return at Surfers Paradise amounting to his worst endurance season since joining the sport.

On Inside Supercars, Whincup admitted to the unimaginable: he was lazy.

"We just left a lot on the table, just took it a little bit easy," he said.

"(We were) a little bit complacent, thought we'd cruise in and cruise out but it wasn't the case.

"We could have done a lot more last year ... mainly beforehand.

"Did we prepare well enough? No, no we didn't.

"We'll get back to where we need to be ... it won't happen this year."

In Whincup's favour is an impressive record heading into the longer races.

The 33-year-old has never lost a championship when he's come to Sandown leading the pack.

He will also enjoy continuity in the No.88 car.

While half the field have new co-pilots, Dumbrell returns to partner Whinchup for the fifth straight year.

Whincup said he wasn't part of the decision for Dumbrell to return to the role but he was confident they could right the wrongs of last year.

"PD has done such a good job in the past it's his option," he said.

"We've given ourselves a kick up the bum this year to make sure we don't have another 2015."