Was Crocodile stronger at Marineford? Or was he holding back in Alabasta?

 During the Alabasta arc, Crocodile displayed a level of power that was initially considered overwhelming by the Straw Hat Pirates. He possessed the Logia-type Devil Fruit called the Suna Suna no Mi (Sand-Sand Fruit), which granted him the ability to control and transform into sand. He had a reputation as a Shichibukai and controlled the desert kingdom of Alabasta from the shadows. His strength was showcased through his battles with Luffy and others. At Marineford, Crocodile was present as part of the war that took place at Marine Headquarters. While he did participate in the battle, he didn't display the same level of dominance as some other powerful characters present. This has led fans to speculate that he might not have been as strong as initially portrayed in Alabasta. It's important to note that power scaling and character abilities can be subject to interpretation and development by the author. Oda often keeps details deliberately open-ended to keep the story intriguing.

Can petroleum-based technology be further improved?

 While petroleum-based technology can certainly be improved, it is important to recognize that our reliance on fossil fuels like petroleum is not sustainable in the long term. As such, it is important to invest in and develop renewable forms of energy in order to reduce our dependence on fossil fuels and protect the environment. There are many exciting developments happening in the field of renewable energy, and it is important to continue to support and invest in these technologies in order to move towards a more sustainable future.