The Melbourne squad faced a challenging lead up to the new season having been forced to return to Holden Commodores following Volvo's sudden withdrawal from the sport last year.
Despite the manufacturer switch, GRM has offered a glimpse into its potential with Tander sixth and team-mate James Moffat 10th in the championship standings after three rounds.
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Tander is just 124 points adrift of championship leader Fabian Coulthard after an impressive WD-40 Phillip Island 500 that saw the veteran convert a 20th in qualifying to third and seventh in the two 250km heats.
His pace was backed up by Moffat who enjoyed a run to fourth in Race 6.
The former Walkinshaw Racing driver admits he has been surprised by his start to the campaign given the team is only at the start of its development.
“There is still a long way to go and a lot of work to do but we are ahead of expectations,” Tander told Speedcafe.com.
“If you look at the results we will definitely take that as we are still early in our program.
“I think there is more to come overall in terms of the whole package.
“We are seriously happy to be as in touch as we are.
“We know we will be strong in the second half of the year, so for us to remain in touch while the super teams are not scoring as many points as they should, is going to give us a good chance at the end of the year.
“We will keep working at it and I'm sure we will get what we need, so we will just keep chipping away.”
Tander's run of form has arrived ahead of his home race at Perth's Barbagallo Raceway next weekend.
The 2007 Supercars champion believes the circuit's abrasive surface will benefit the GRM Commodore that has proved to be kind on tyres.
“I think one of the things the car does pretty well is look after its tyres very well,” he added.
“That is certainly going to help going to Perth.
“Perth is such a different event because the surface is unlike anywhere we go.
“It is a bit of a lottery but I think we are in pretty good shape. I think it will be less of a challenge than what Phillip Island was.
“It is going to be different but equally as exciting with the tyre degradation so I think we will be in the mix.
“Whether we can get ourselves on the podium I'm not sure, but a couple of top fives will be good.”
Tander and the GRM squad will head west to the Perth Super Sprint for round four of the championship from May 5-7.