The Spanish Grand Prix is a hefty old benchmark for the teams. Not only does it show how far they've come against each other since the start of the season in Melbourne, it shows how far they've come against themselves, when they compare results to their test times in March.
Normally the Spanish sun would be beating down on the Circuit de Catalunya doing its best to obscure the comparisons with two months ago. But this weekend looks like being unnaturally cold with temperatures (forecast on Tuesday) to be around 19C. It's still warmer than March but not as much as you might expect.
So the mirror is there to be held up; and with an abnormal three-week gap since the last race in Bahrain, the scope for development work has been huge. Normally there is a raft of modifications that are lined up to be bolted on the car at the first European race, but there's been more time for fabrication than usual.
Thus Friday should be a very busy affair up and down the pitlane as everybody's great new evolution and aero tweak is attached to the car. And to help evaluate them, as well as give the spectators more on-track action, the teams will be getting an extra set of tyres on Friday as Pirelli's Paul Hembery explained: "We'll be supplying an extra set of prototype hard compound tyres for free practice, which will hopefully ensure that all the cars run throughout these sessions. It's something we wanted to do to encourage all the teams to run as much as possible right from the start, especially with the rookie drivers, to give fans the spectacle they deserve."
That's not the only development for Spain. Pirelli have changed the specification of their hard tyre and made it harder, more like the hard from last year. However the Pirelli motorsport boss is very keen to emphasize that it was something they were going to do anyway and that they're not just reacting to pressure from Bernie's favourite team Red Bull.
"We're introducing a revised version of our hard tyre in Spain," said Paul. "This new tyre gives us a wider working temperature window - although it delivers a little bit less in terms of pure performance - but it should allow the teams to envisage an even wider variety of race strategies than before in combination with the other compounds, which remain unchanged this year."
Teams will qualify on the medium and race on the hard tyre. Last year that strategy produced an epic fight between Fernando Alonso at his home race and some stern resistance from Pastor Maldonado who clung onto the lead, producing the F1 drive of his life. Unlike China in 2013 the DRS made overtaking possible but not inevitable and Maldonado held on for a memorable debut win and as many points as Williams had scored in the previous season.
The win was soured somewhat by the subsequent fire generated by Bruno Senna's Williams and the garage going up in flames. But it showed the F1 teams rallying together and all pitching in to try and help out. This year another win is about as unlikely as another fire; the Williams team look like they sorely miss the engineering guidance of Mark Gillan.
McLaren are the team who arrive at the Circuit de Catalunya with the most expectation on their shoulders. Another faint result for Button and Perez and the team can kiss goodbye to any pretensions of a title campaign, they're just going to be in it for the highest finish they can get. Right now, a series of unfortunate incidents for Vijay Mallya's team have left McLaren in the vicinity of Force India, when really they should have been trailing them in a firm sixth place.
Their relative performance against Force India will be an indication of progress, or lack of it, as the engineering budget for the Silverstone team will be considerably less.
Mercedes want to improve their race pace and their rear tyre cossetting - they know they can rock up and qualify well. For Ferrari it's the reverse, their race pace is good, if not the best, they just can't qualify as high as they need to, to get (and stay) in front of Vettel. The same for Lotus - they have great race pace which is compromised by starting from the third, fourth or fifth rows and having to fight their way through traffic.
Red Bull are still the team to beat and have traditionally done well on the long, high-speed turns of Barcelona. Up to now their problem has been that they can't get their tyres to last as long as Ferrari and Lotus, but with a new harder hard tyre, they may have been handed an advantage.
Such is the knowledge and the experience of the teams in Barcelona that cars performance will be maximised and they should line up two by two on the grid. Any driver who can put a row in between them and their team-mate has done a brilliant job, or their team-mate a stinker. Or the unpredictable Barcelona wind has got to them.
There will be a lot of focus on the briefly fractious Perez vs Button relationship this weekend (with the cars likely to be close). Button has to shoulder a lot of the blame for Bahrain for not getting out of the way when Perez was being held up and able to run far longer. Jenson isn't likely to make the same mistake twice. Checo did what he was told and got his elbows out - and big credit to McLaren for letting him do just that.
Vettel vs Webber may well be rejoined as Mark goes well in Barca, and of course last time out Nico outqualified Lewis. Kimi Raikkonen's had it pretty easy against Romain Grosjean this year, but now Romain is going to have virtually the same package as Kimi in Barcelona, so like can be compared with like. Lotus know that they will only hang onto Raikkonen (whose contract is up at the end of the year) if they give him a competitive car. Will that extend to handing places to Kimi now that Romain is so far back in the championship - that may be a question we'll soon find the answer to.