For the last two races Sauber has been teasing us with messages on their cars.
China: out of the blue

Bahrain: True blue

We know they will have the sponsor on their car starting from the Spanish GP. But we wouldn’t be fanatics if we wouldn’t discuss it earlier. I found an interesting Dutch link and I transelated it for you fine people. It suggests that it’s a deal with Russian businessman Roman Abramovits owner of Chelsea football club.
Link: http://www.gppits.net/nieuws/nieuwe_sponsor_sauber1/
Translation:
Saubers new sponsor
The Sauber F1 Team has attracted a new big sponsor but has been quite mysterious about the name of their new sponsor. Sauber has been driving around this weekend with the text ‘’True Blue’’ promptly on the engine cover. It seems Sauber wants to start speculations.
It is assumed that Sauber has found a sponsor in the rich Russian businessman Roman Abramovitsj. Abramovitsj is owner of the Chelsea and would like to attract more attention trough Sauber. This phenomena isn’t entirely new, the English premier-league club has been doing the same with Caterham F1
Also former Williams sponsor AT&T, the American telecom giant is connected to sauber. AT&T loaded several millions in Formula 1 until last year. Yet this deal seems highly unlikely because Sauber already has a major Mexican Telecom Sponsor Telmex.
Soon Sauber will announce witch sponsor it realy is. We’ll keep you posted at GPPits.net.
I can’t vouch for the reliability of this link
Any of you have another theory?