Luigi Mazzalo was part of Ferrari's test team up until 2007. During his time at Maranello, his job was to go through testing times and dissect them for his team to give them an idea of what other teams were doing, as close as one could, given the variables during testing.
He has done an analysis of the last Barcelona test. The article in full, which is in Italian can be read here
I'm pasting the two bits of relevant information from his article. The first is a chart of teams as he sees them and their respective pace.
The second chart is of tire degradation on respective teams.
<table id="wp-table-reloaded-id-26-no-1" class="wp-table-reloaded wp-table-reloaded-id-26"><thead><tr class="row-1 odd"><th class="column-1">TEAM </th><th class="column-2">BEST LAPTIME</th><th class="column-3">FUEL LOAD IPOTIZZATO</th><th class="column-4">BEST LAPTIME NO FUEL</th> </tr> </thead> <tbody> <tr class="row-2 even"> <td class="column-1">Red Bull Renault</td><td class="column-2">1:22.6</td><td class="column-3">50 Kg</td><td class="column-4">1:20.9</td> </tr> <tr class="row-3 odd"> <td class="column-1">McLaren Mercedes</td><td class="column-2">1:22.1</td><td class="column-3">20 Kg</td><td class="column-4">1:21.4</td> </tr> <tr class="row-4 even"> <td class="column-1">Ferrari</td><td class="column-2">1:22.2</td><td class="column-3">20 Kg</td><td class="column-4">1:21.5</td> </tr> <tr class="row-5 odd"> <td class="column-1">AMG Mercedes</td><td class="column-2">1:22.9</td><td class="column-3">40 Kg</td><td class="column-4">1:21.5</td> </tr> <tr class="row-6 even"> <td class="column-1">Lotus Renault</td><td class="column-2">1:22.0</td><td class="column-3">20 Kg</td><td class="column-4">1:21.3</td> </tr> <tr class="row-7 odd"> <td class="column-1">Force India Mercedes</td><td class="column-2">1:22.3</td><td class="column-3">20 Kg</td><td class="column-4">1.21.6</td> </tr> <tr class="row-8 even"> <td class="column-1">Sauber Ferrari</td><td class="column-2">1:22.0</td><td class="column-3">20 Kg</td><td class="column-4">1:21.6</td> </tr> <tr class="row-9 odd"> <td class="column-1">Toro Rosso Ferrari</td><td class="column-2">1:22.1</td><td class="column-3">10 Kg</td><td class="column-4">1:21.7</td> </tr> <tr class="row-10 even"> <td class="column-1">Williams Renault</td><td class="column-2">1:22.2</td><td class="column-3">20 Kg</td><td class="column-4">1:21.5</td> </tr> <tr class="row-11 odd"> <td class="column-1">Caterham Renault</td><td class="column-2">1:22.6</td><td class="column-3">10 Kg</td><td class="column-4">1:22.3</td></tr></tbody></table>
<table id="wp-table-reloaded-id-27-no-1" class="wp-table-reloaded wp-table-reloaded-id-27"><thead><tr class="row-1 odd"><th class="column-1">TEAM</th><th class="column-2">DEGRADO</th> </tr> </thead> <tbody> <tr class="row-2 even"> <td class="column-1">Red Bull Renault</td><td class="column-2">1</td> </tr> <tr class="row-3 odd"> <td class="column-1">McLaren Mercedes</td><td class="column-2">2</td> </tr> <tr class="row-4 even"> <td class="column-1">Ferrari</td><td class="column-2">3</td> </tr> <tr class="row-5 odd"> <td class="column-1">AMG Mercedes</td><td class="column-2">4</td> </tr> <tr class="row-6 even"> <td class="column-1">Lotus Renault</td><td class="column-2">2</td> </tr> <tr class="row-7 odd"> <td class="column-1">Force India Mercedes</td><td class="column-2">2</td> </tr> <tr class="row-8 even"> <td class="column-1">Sauber Ferrari</td><td class="column-2">3</td> </tr> <tr class="row-9 odd"> <td class="column-1">Toro Rosso Ferrari</td><td class="column-2">2</td> </tr> <tr class="row-10 even"> <td class="column-1">Williams Renault</td><td class="column-2">3</td> </tr> <tr class="row-11 odd"> <td class="column-1">Caterham Renault</td><td class="column-2">3</td></tr></tbody></table>
All this is done with the assumption that every team was running legal, no team ran under weight to attract headline times and sponsors and race simulations were done without using DRS.
Andrew Benson, BBC Sport's chief F1 writer has done a similar analysis. The most puzzling thing to come out from his analysis is-that the fastest man during winter testing, counting all the laps done by all the drivers, is Fernando Alonso. If you average out all the laps of all drivers, Alonso's time is 0.3secs faster than anyone else:S
The full article;
Ferrari's fate the foremost of many unknowns
Kimi Raikkonen was to the point, as ever. The man who returns to Formula 1 this season after two years in rallying was asked how he felt the teams compared. "In two weeks we know," the Lotus driver said. "There is no point to guess here. I don't know who's going to be fastest. Nobody knows."
And yet, and yet. If you average out Alonso's lap times over the whole of winter testing, guess what? He is the fastest of all - by 0.3secs. No wonder Webber says: "The mystery is the Ferrari."