Renault advisor Alain Prost hailed the French team's progress this year but believes the bulk of its improvement will be seen in 2019.
There was festive atmosphere in the Renault camp after the Abu Dhabi Grand Prix as the French outfit celebrated wrestling P6 in the Constructors' standings from Toro Rosso, an achievement made possible by Nico Hulkenberg's sixth place finish on Sunday.
Renault fulfilled its target in a season which saw the manufacturer ramp up its resources both in Enstone and Viry-Chatillon.
Progress has been incremental however, says Alain Prost, and will continue next year.
But the real step forward should occur in 2019 according to the four-time world champion and Renault ambassador.
"I always said that progress will be slower than people think," Prost told Sky F1 after yesterdays' race.
"Maybe slower, maybe better. We can see on the engine side this year, we have improved. Maybe nobody saw it but it was better than we thought. But when you improve a little bit too much you have reliability problems.
"It's not the same on the chassis side. We have acquired a lot of people, especially on the aero side that will give the maximum in my opinion, not next year, but in two years.
"Next year the point is to make a big progression, not only in terms of ranking, because you can finish fourth and still be two seconds a lap slower than Mercedes and Ferrari. That would not be positive, we need to catch them slowly.
"There's no point saying today where we are going to be next year, it's too soon."
Prost admitted the balance between performance and reliability was a delicate one to achieve, as Renault's numerous engine failures in the latter part of the season attest.
"The balance is very complex with these engines. For example, we brought a new MGU-H this year. Everything looked okay but maybe it was a bit too soon, but we wanted to get performance or else there's no point.
"At least we learned about it. And what we learned this year could be positive for next year but it was quite difficult during the year. There was also a supplier problem which can happen in racing.
"That's why the performance has to be stable and consistent. There's no way you can gain from this year to next year maybe two seconds a lap, absolutely no way.
"How much it will be, I don't know, it's always a compromise."
