Bob Bell says Renault remains on track to race to podium finishes in 2019.
The French team has made progress this year, and signed up Red Bull's Mexico GP pole sitter Daniel Ricciardo for 2019.
"Everyone has highlighted our progress on the track," technical boss Bell told Ouest-France.
"We wanted to be fourth, we are, but we have to be careful. Over the last races, our car was not fast enough and though we have progressed, we are still quite far from the top three."
Bell says Renault wanted to make better progress in 2018 relative to the top teams Mercedes, Ferrari and Red Bull.
"Modern F1 is very much aero, engine and tyre management. We did a lot of work on aero and perhaps not enough on the engine compared to the others.
"There's no magic formula. It's very hard to make progress," he said.
However, Bell insists that Renault is sticking with the longer term plan.
"We're looking more two or three years ahead," he said. "We are working hard on the 2019 car, and also on the 2020 and 2021 cars. And I am very satisfied with our progress.
"If you look at our facilities, our technologies, the way we work -- all of these details are starting to work very well," Bell explained. "We're just not seeing all of it on the track yet.
"But I think that next year we will be able to fight for the podium and get closer to the top teams."
