Kimi Raikkonen's Australian Grand Prix victory announced Lotus as a championship contender this year.
The team then slipped back in Malaysia, finishing only sixth and seventh, with Grosjean ahead.
Lotus remains second in the constructors' championship, 26 points behind Red Bull, while Raikkonen is Sebastian Vettel's nearest rival in the drivers' table, nine points adrift.
Asked if he was confident Lotus could stay in the title hunt, Grosjean said he was confident in the team's capabilities but unsure about its resources.
"It depends on the money that we have. That is the key in F1," he said.
"We know we have good people, we know they are able to do a race winning car, we know that on development and on factory tools we are there.
"But then again everything is a question of what you can put into it."
Grosjean said the team's winning start "should" help bring in more funding.
"Hopefully we get more sponsors, so more development and then more wins and then more sponsors," he said. "It's a cycle."
AUTOSPORT understands the team was working on a major sponsorship deal in the second half of last year, but nothing has come together so far.