1. Complaints upheld
The advertisers said much research had gone into the development of Optimax. They explained that detailed research on fuel technology for motorsport had enabled their scientists to gain a unique understanding of how power could be delivered instantly to the engine from the fuel, as demanded by racing cars. The advertisers stated that their scientists had used their knowledge to develop Shell Optimax, which was designed to give the same benefit to road cars. The advertisers said Shell Optimax had been developed to address three key problems associated with the delivery of fuel to engines: the deposits left on and around the inlet valve, slow fuel vaporisation and wrong fuel quality, all of which automatically reduced the power and performance of the engine. They maintained that the new fuel formulation had been demonstrated to increase the performance of cars in tests on acceleration, power benefit and engine responsiveness, and supported that with evidence.

The Authority obtained expert advice. It understood that the evidence supplied by the advertisers showed that changing to a higher octane fuel could create a small but variable increase in the power and acceleration in some, but not all, cars. The Authority considered that the claims implied that changing to Optimax from other unleaded fuel would significantly and immediately increase the power output of any car under rapid acceleration. Because the advertisers had not shown with documentary evidence that Shell Optimax would affect all cars by increasing their power and acceleration rates, the Authority considered the claim misleading. It welcomed the advertisers' assurance that they would amend future advertisements to avoid the implication that the claim applied to all cars.

2. Complaint upheld
The advertisers believed that Shell Optimax was the "best performance unleaded" because it had the highest specified octane level in the UK and the most effective deposit-removing capacity of any fuel in the UK. They provided several tests to support their claims. The Authority obtained expert advice. It considered that the claim "best performance unleaded" suggested that the advertisers' fuel produced better performance results than all other unleaded fuels. Because the advertisers did not provide sufficient evidence that compared the performance of vehicles using Optimax with those using competitive super unleaded commercial petrol, the Authority considered that the advertisers had not shown that Optimax produced better results than all other unleaded fuels, the Authority told the advertisers to delete the claim until they could substantiate it.

3. Complaint not upheld
The advertisers maintained that Optimax was formulated with an effective detergent additive, which removed deposits from the engine to improve performance, and that, because the formulation did not contain large amounts of the materials that formed deposits, Optimax kept the engine clean. The advertisers provided several tests to support the claim. The Authority sought expert advice. It understood that the evidence supplied showed that the detergent additive removed a significant proportion of deposits on the inlet valve of cars when driven for several thousand kilometres using Optimax. It considered that the advertisers had substantiated the claim "If deposits have already formed, Shell Optimax's detergent action will loosen and dissolve the particles, removing them from the valves, so the more you use Shell Optimax the cleaner your engine becomes" and did not uphold the complaint.

4. Complaint upheld
The advertisers said the diagram pictured the performance benefits achieved by a car when using Shell Optimax compared with an identical car using normal unleaded petrol. They maintained that Optimax enabled engines to perform more effectively because of its intrinsic cleanliness, effective cleaning ability and its anti-corrosion package. They provided evidence to support the performance claims. The Authority sought expert advice. It understood that the evidence supplied by the advertisers had proved the increased acceleration claims for some, but not all, cars. The Authority considered that the diagram, which compared the performance of two identical cars using different fuels, implied that using Shell Optimax alone would enable a car to overtake faster than one using normal unleaded fuel. Furthermore, it was concerned that the claims "You'll feel the difference straight away" and "it improves your vehicle's responsiveness from the moment you start using it" suggested that the engine performance of all cars would be immediately improved by using Optimax instead of normal unleaded fuel. The Authority considered that the diagram, in conjunction with the claims, was likely to mislead readers to think that Optimax would improve performance and acceleration of all cars. It welcomed the advertisers' decision to withdraw the leaflets and amend future advertisements by deleting the diagram and supporting claims from future advertisements.

5. Complaint upheld
The advertisers maintained that the diagram and wording of the leaflet was clear and related to the benefits of using Optimax. They pointed out that they had made no statement or claim about improving the driving performance of inexperienced drivers. The Authority was concerned that the claim "crucially, it can help you to manoeuvre safely by delivering a smooth burst of power, just when you need it most" implied merely that by using Optimax it was possible to drive more safely. It considered that the advertisement was likely to encourage all drivers, both experienced and inexperienced, to think they could overtake more safely when using Shell Optimax. The Authority welcomed the advertisers' decision to withdraw the leaflets and amend future advertisements by deleting the claim ""crucially, it can help you to manoeuvre safely" before advertising again.