The two-time World Champion out qualified his McLaren team-mate in each of the 21 races in the 2018 season.
He also managed to do so in the last five races of 2017, taking the run to 26 consecutive race weekends.
The Spaniard believes that his extracurricular activities have played a role in achieving this feat.
“It’s difficult to know exactly your speed in the car,” Alonso said.
“You only can follow the numbers, and this year it has been my best year by far in terms of qualifying battles.
“So, I feel I’m competitive and I’m fast.
“Probably, testing day in IndyCar and the WEC programme this year, I feel better driver, or a more complete driver.
A veteran of 311 starts in Formula 1, Alonso said that he has learnt a few tricks in the different disciplines, which he brought back to the F1 paddock.
“I understand more the behaviour of the cars, other driving techniques, other ways of saving energy, saving the tyres,” he explained.
“So, you have more information from the outside and other engineers, other points of view, that maybe makes you better, or [provides] a wider views of motorsport.
“Probably when you jump in the Formula 1 car, you have an extra opinion even if it’s not totally useful in a Formula 1 car.
“The overall concepts of different philosophies, I think it helps you as a driver.
Neither of the McLaren men are in the sport for 2019, with Alonso focussing on his WEC super-season and the Indy500 in May.
Stoffel Vandoorne, on the other hand, has gone green. He will race in the Formula E series for the 2018/19 season.