This comparison is wrong. You want CO2 per distance, not CO2 per liter. From these numbers if it could go either way. If the diesel engine gets 10% more distance/liter then it's worse than an Otto engine, but if it gets 20% more distance/liter then it's cleaner than an Otto engine. CO2/liter tells us very little.

However, what is certain is that the CO2 savings from diesel is small and certainly less than 50%. That's not going to get us where we need to go in terms of carbon emissions.