Helio Castroneves' dominating victory at the Texas Motor Speedway last weekend has been somewhat tainted by the news that his race-winning #3 Penske car failed post-race technical inspection following the Firestone 550 on Saturday night.

The car was found to breach the rule about underwing settings allowable at the 1.5-mile high-banked oval circuit, but the team denied reports that this meant the #3 car might any had an aerodynamic advantage during the two-hour race or that the illegal setting might have allowed Castroneves to run a higher line than his rivals during the race.

"The way Helio's car raced did not provide any advantage as a lower diffuser height actually adds drag and reduces downforce," insisted Tim Cindric, the president of Penske Racing, adding that the team had confirmed this in wind tunnel tests on Monday.

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However, extra downforce might have helped the car achieve better mileage on each set of tyres before degradation forced a pit stop, in a race that was ultimately dominated by long green flag stints and a focus on attaining optimum pit stop strategies.

"Obviously, we are very disappointed that the #3 car did not pass post-race inspection after Saturday's race at Texas," he said, explaining that the required 7.6-inch measurement on the diffuser exit had been under by just 0.025 inches.

"We neglected to tighten the braces that position the rear of the diffuser following pre-race inspection," Cindric added.

The post-race technical inspection doesn't mean that Castroneves loses the win - the first for Penske in an unusually lean start to 2013 for the team - and instead the penalties imposed are limited to financial fines and docked points.

Team Penske will have to pay up $35,000 for the infraction, and the #3 will also lose 15 entrant points. Castroneves himself is not fined and does not lose any points in the drivers championship.

Last year, the 2012 race-winner Justin Wilson was also penalised for a technical violation in the race after stewards failed to spot that his Dale Coyne Racing car was using aerodynamic parts that were disallowed by late rule changes just a day before the start of the event. Wilson lost five points in the championship for that, while the team had been penalised $7,000.

Penske Racing itself has been in the news already in 2013 after being penalised by NASCAR for running illegal rear suspension components in the Sprint Cup Series cars of champion Brad Keselowski and his team mate Joey Logano. Penske won a reduction to the penalties on appeal, and similarly has the right of appeal over the Texas IndyCar infraction.