Lewis Hamilton, a title favourite with the dominant team Mercedes, downplayed the German squad's superiority when he said at Sepang: "I'm sure Renault have not turned their engine up to max.
"It's the same with Ferrari. If you look at their apex speed, they have a good car."
According to Spaniard Alonso, however, that's not right. "As far as the electrical side, yes, we are using the full power.
"But in the early laps in Melbourne we had a problem that we were blocked and so it didn't work fully," he is quoted by El Mundo Deportivo.
Alonso is referring to the energy-recovery side of the new 'power unit' that, in the opening phase of a grand prix, is automatically 'blocked' by the FIA.
But the Ferrari-powered cars in Melbourne were without up to 100 horse power for the entire first stint until the pitstop, due to an FIA glitch.
It is also clear that Ferrari's 'power unit' is up to 13 kilograms overweight.
Alonso has won at Sepang in a Renault, a McLaren and a Ferrari, but he effectively ruled out a repeat of his surprise 2012 win this weekend.
"This is formula one and anything can happen," he is quoted by the EFE news agency, "but I think what we saw in 2012 was once in a lifetime."
Beyond that, he is not willing to talk too much about his 2014 prospects.
"If I say I am happy with fourth place, someone will say that I am no longer hungry for results," said Alonso.
"And if I say that I am not happy, someone will have something to say about that too."