After a tumultuous partnership was ended with McLaren at the end of 2018, Honda switched to Red Bull for last season, enjoying a stunning improvement in performance and reliability.
It resulted in Verstappen claiming three wins and six additional podiums that helped propel him to third in the drivers' championship behind Mercedes duo Lewis Hamilton and Valtteri Bottas.
Following the RB16's bulletproof reliability over the first pre-season test at Barcelona's Circuit de Catalunya, with Verstappen clocking up 254 laps across his day and a half in the car, he said: "They (Honda) are pushing flat out.
"Of course, you always want improvements. Improvements definitely have been made compared to last year as well.
"What I like is that what they show, what they project, always happens, so I'm very confident it will be the same this year again.
"Everything is heading in the right direction, but the others will also be pushing flat out so we just have to try and work harder."
Verstappen is hoping to avoid engine penalties this season, as was the case last year, although he concedes it was with good reason.
Each power unit will be required to last seven grands prix again this year should the calendar be 21 races, rather than the planned 22 due to the Coronavirus outbreak forcing China's postponement.
Verstappen added: "Last year we only took engines because they had performance upgrades, and quite big ones, so that was the reason to take those engines.
"Of course, this year we will try not to take any penalties, but things are running very smooth and that's all we can do.
"In terms of mileage, it's all going well. Throughout the winter we've been looking to make it through those seven weekends.
"So far we've not run full power modes, but it's all running smoothly, and that's exactly what you want."
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