Sebastian Vettel said he will not publicly compare Aston Martin's Mercedes engine to Ferrari's out of respect to his former team.
Vettel joined Aston Martin for its return F1 project this year, after his six-year stint with Ferrari came to an end. It is his first time driving a Mercedes power unit -- the German manufacturer has won every championship since the introduction of V6 turbo engines in 2014.
Vettel has been driving his new car at preseason testing in Bahrain.
When asked to compare the Mercedes to Ferrari, he said: "It's obviously different but I'm not going to compare, just out of respect to different manufacturers.
"It's something that I've never done in the past and I won't do now."
Vettel struggled in his final years at Ferrari, with a series of spins highlighting his unease with the stability of the Italian team's cars. The four-time world champion was cagey over the details of his driving style but said he feels confident the same issues will not repeat themselves this year.
"Again, I will not disclose too many details. But we will have the car that we have underneath us and we have to adapt, so I think that's not a problem. I'm sure it's fine.
"We work very hard to ensure we have a quick car. It will be a long year, a tricky year to split the resources for this year and next year. Lots of challenges but the main challenge right now is to have a decent test."
Aston Martin's opening test has seen two lengthy delays in the garage, but Vettel is encouraged by what he's seen from the car so far.
"The last 24 hours have certainly been very busy for myself, for everyone in the garage, for the whole team. Unfortunately we didn't have a very productive morning, we had an issue with the gearbox we had to change and that cost a bit of time.
"That's what happened and unfortunately we didn't get a lot of laps in. So this morning was not of great use in terms of track time.
"Yesterday though was very interesting. The car feels very promising but there's still a lot of things I need to get used to. The car is different to what I ran [last year] and it's a different power unit as well so everything feels a bit different and takes a little bit of getting used to."
After testing concludes on Sunday, the Formula One season will begin with the Bahrain Grand Prix on March 28.