The Silverstone-based team concedes that this year’s car has been weak in that area, which is why it endured such a difficult weekend at Monza.
Fernando Alonso had his least competitive showing of the season at the Italian Grand Prix, struggling to finish ninth, while Lance Stroll was out of the points in 16th.
Alonso has urged the team to address efficiency, and McCullough agrees that it is a priority.
“Fernando touched on the efficiency of the car,” said McCullough when asked about the issue by Autosport.
“It is an area where at the start of the year we were definitely one of the slower cars in the straight line.
“We worked on that with the base car, and also the rear wing levels that we brought [to Monza]. It's an area of improvement, and it is an area we need to improve more for next year, that’s clear.”
McCullough conceded that there are unlikely to be changes that will benefit this year’s model, with Las Vegas the key race in the last part of the season that highlights efficiency as much as Spa and Monza.
“The main architecture of the car, the whole car more than just the rear wings, the areas that we've worked on, there are a lot of elements that contribute to the efficiency of the car,” he said.
Source: Autosport