The press ad, created by Lowe London, showed two parallel horseshoe prints and tyre marks and stated: "More horsepower. And a smaller carbon footprint."
The body copy included the text: "It's a fuel made from natural crops that reduces CO2 emissions by up to 70%."
The smallprint included: "Bioethanol consumption does not significantly raise atmospheric levels of CO2".
Three complainants to the Advertising Standards Authority challenged the claim that it "reduces CO2 emissions by up to 70%", while another two also challenged the claim that "bioethanol consumption does not significantly raise atmospheric levels of CO2".
Saab said that because the use of bioethanol E85 consumption reduced CO2 emissions by up to 70%, it followed that it did not significantly raise CO2 levels.
It pointed out that it had not claimed bioethanol did not produce any CO2.
The first issue was not upheld, but the advertising watchdog upheld the second complaint about not significantly raising CO2 levels.
The ASA considered that it was reasonable to make such a claim in a direct comparison with conventional fuel, but noted that it was not presented in this way.
It said that readers were likely to infer that bioethanol did not add a significant amount of CO2 to the atmosphere, but it considered that a 30% net addition was significant and therefore concluded that that claim was likely to mislead.
In a separate adjudication, energy group Areva escaped a ban for its press ad headed: "Our energies have a future. A future without CO2".
The ad, created by Euro RSCG, received a single complaint from Friends of the Earth Europe, which challenged whether the ad gave a misleading impression of the environmental benefits of nuclear energy, particularly in relation to CO2 emissions.
Friends of the Earth also said the claim that "Areva offers its customers solutions for producing and transmitting electricity, while protecting the planet", was misleading because it believed that the majority of the advertiser's business was concerned with nuclear energy production, which had a documented history of causing environmental damage.
The ASA did not uphold either of the issues. It noted that the ad was not focused on nuclear energy only and that that was made clear by references to Areva's commitment to the development of renewable energies.