When using a consensus speed advisory system (CSAS) to recommend speeds for vehicle fleets, challenges often arise regarding the untrustworthiness of the service and the transmission of incorrect data among vehicles. Additionally, existing research mainly focuses on speed advisory scenarios for flat roads. If the speed recommendations for flat roads are applied to sloped roads, vehicles may consume more energy, failing to achieve the optimization goal of minimum energy consumption. To address these issues, this study proposes a blockchain-based consensus speed advisory framework for sloped roads. This framework extends existing CSAS to sloped road scenarios, further solving the problem of optimizing the minimum energy consumption for autonomous vehicles on sloped roads. At the same time, private blockchains and cryptographic primitives are introduced to ensure the trustworthiness of the service and the privacy of data transmission among vehicles. By implementing this framework with Ethereum private blockchains and Truffle, experimental results show that the framework can provide trustworthy consensus speed recommendations in sloped road scenarios and effectively reduce vehicle energy consumption.