Lotus owner Gerard Lopez is of the opinion that the Enstone team have improved by about two seconds per lap thanks to the progress Renault have made with their power units of late.
Lotus received a significant upgrade from the French engine manufacturer before last week's Chinese Grand Prix, which are believed to be similar to what Red Bull have been running of late.
The engine upgrades had an immediate effect on Lotus' performance, with Romain Grosjean reaching Q3 for the first time this year and seemed like he would score some valuable Constructors' Championship points before a gearbox problem forced him into retirement.
"We saw a clear step up from Renault's side in China," Lopez told Autosport after the Chinese Grand Prix.
"The guys are almost talking about two seconds, which is huge.
"The stopwatch doesn't lie - we moved two seconds forward in terms of performance.
"The car is good. Romain had some diffuser issues on Saturday, but based on lap times and derivatives of that, we probably should have gone for P6 [in qualifying] if we hadn't have had any issues.
"That is really where we believe the car belongs, despite knowing the Mercedes engine cars don't even need DRS to go around us.
"At the same time what is positive is the pace seems to be there."
Despite their recent improvements, Lopez admitted that the start of the season has been far more difficult for Lotus than they imagined.
"We didn't expect to have the engine issues we've been having," he told Autosport.
"We came out of the windtunnel essentially knowing we had a really good car.
"But the problem is when you start putting things down on the track, unless you can actually lap you can't do any set-up work.
"So we've had huge, huge issues and delays because of lack of lapping essentially.
"We really reached a peak of negativity after the race in Bahrain where two engines blew [in testing] and there was nothing we could do.
"That was really a point where, in a positive way, we put a stop to certain things we were doing and said 'we just can't afford to do this any more'.
"Renault is promising a fairly interesting step up for Barcelona.
"We're pretty hopeful we start coming into the top 10, and from then on it's fighting it out with whoever is there.
"Ever since I saw the issues we were having with the power unit, I've essentially said our first race is going to be Barcelona, and I stick to that."