Having forged a close working relationship with Ferrari's fuel and lubricants partner Shell since joining the squad in 2021, his understanding of the complexities behind what powers his engines has grown considerably.
So, as we sit chatting inside the Shell track lab that is housed inside the Ferrari garage at every F1 race on the calendar, he is quick to respond as I enquire about whether or not it is true a driver can be identified just from the chemical composition of an oil sample from his engine.
"That's a myth," he laughs. "We are actually driving within a tenth of a second of each other. So, to actually find any differences on fuel or oil, or how you treat that engine from driving, is not something that you can do.
"But we do have difference in consumption Charles [Leclerc] and I, because of my driving style.
"Normally for a race, maybe I need half a kilo to a kilo less fuel than him because of my driving style. But I don't think my driving style affects the condition of the fuel after the race."
Working together
While such tiny fuel details can be important in an F1 world where marginal gains are the name of the game, it's not the here and now that has especially grabbed Sainz's attention.
Instead, it's F1's looming move towards fully sustainable fuel – and the potential impact that will have on car performance – that Sainz is paying more attention to.
And it is little wonder because getting the fuel and engine rules right from 2026 will be critical to any team's title hopes.
"It has obviously become more of an interest, getting to know this partnership and getting to work with Shell the last three years I'm in Ferrari," he said.
"Plus getting to know all the effort and everything that they put into F1, particularly obviously with Ferrari.
"When we changed to the 10% ethanol fuel [for 2022], I remember there was a drop in performance expected. All drivers were worried, because they said the engines were going to drop by 20/30 horsepower.
"I wanted to know what Shell was going to do with the fuel and how they were going to help us to make sure that we didn't lose the power. And I remember that year, we actually did a pretty big step jump up in performance thanks to them!
"So now the next big challenge will be the 2026 set of regulations and going 100% sustainable fuels.
"And I think this is where my interest is going to shift more now; to follow the development and see how also, with the designing of the rules, it's going to play out."
Since arriving at Ferrari, the closeness of the relationship between the Prancing Horse and Shell has been one of the big surprises for Sainz.
And although it is not an area that has a direct input into performance gains each race weekend, because F1 currently has a freeze on fuel development, that it not to say he doesn't follow operations quite closely.
For with fuel and oil samples taken after each session for analysis to try to get some early warning signs of any trouble inside the engines, the fuel and oil dialogue is constant.
"That's why after every session we give our feedback to the engineers, and then after every single run that we come into the box, they take a sample of the fuel and oil," added Sainz.
"They take a sample, analyse it, check that everything is okay, and then next one. This is repetitive, repetitive. And it's going on the whole year.
"So, you can imagine the number of samples and the number of things that we have been doing together is huge. And it just helps us to perform better and to get more of a routine inside the team to perform consistently."
Shell's delivery manager of motorsport Valeria Loreti says that working with a driver like Sainz has been a privilege.
"He is very much into details," she explained. "And whenever we have a chance to chat, he's always curious to learn and to understand the technicalities.
"I think with Shell and Ferrari, we have this striving for performance and pushing the boundaries, because the investment in motorsport R&D is really a free place to experiment and to learn something new. It is the basis of our future development."
Pushing performance boundaries
As F1 heads towards new rules 2026, Sainz is well aware of the value that will come from keeping close tabs on how progress is going between Shell and Ferrari, especially when it comes close to homing in on final specs.
"You're always trying to find that fine line between performance and reliability," he said. "You probably know that you could extract five more horsepower from an engine pushing it a bit more during the season, but it might give you two or three DNFs.
"So, is it worth that five to 10 horsepower? Probably not because the number of points you lose is quite hard. But this is mainly down to engineering and mainly down to the team deciding where to find that fine line of performance versus reliability, because it's always a trade.
"You can never have the most performant engine and at the same time be super reliable. But that's where everyone has to work together on clear targets, clear expectations, and where you want to play the performance."
Loreti also thinks that as F1 transitions towards 2026, the balance between power and reliability has an extra element now.
"They have been always the key targets, and obviously you will come to a limit where more performance means less efficiency and vice versa," she added.
"But now this picture is becoming more complex because you're adding a new dimension, which is the sustainability.
"So, it makes the equation even more difficult to solve and, as a scientist, more challenging. But that is what really pushes us."
Keeping the spectacle
Just as F1 sees tremendous value in the switch to sustainable fuel for 2026, the message is that those who follow the action should have nothing to fear as there is no reason to suggest that it will make things any less exciting.
Asked about where the balance should lie between sustainability aims and the entertainment factor, Sainz said: "I think with a good plan, you can achieve both.
"I think everyone has a good grasp on how to put together the best set of regulations to have both sustainability and a show, and that is what F1 should try and achieve.
"At the same time, I do believe everyone should be a pioneer in development.
"I will always be in support of being pioneers in developing sustainable fuels and a sustainable world. But at the same time, without forgetting what makes fans fall in love with the sport.
"Finding the compromise for these two things is exactly what everyone should try and do, and everyone is trying to do."
It is also a move that excites Shell.
As Loreti explained: "Everyone is driving a change in sustainability. In the future, the world will be more sustainable in the world of energy, and we want to be leading this revolution.
"We think that there will be no silver bullets. There will be multiple energy carriers and energy solutions that will help us win with the energy transition.
"But having the opportunity to demonstrate that advanced sustainable fuel, that it still delivers performance and it's something that can be done and generate ideas and future technologies for other products, is another piece of the jigsaw."
