According to the RAM Promaster Owner’s Manual you should only use Regular gasoline.
While the technical information posted by group members and administrators can be helpful note that the members electing to make use of the same are doing so at their own risk. Members are encouraged to contact Winnebago, FCA, and/or the component manufacturers for the best information. We cannot guarantee that the information presented here is 100% accurate. Most of it is copied from other resources or compiled from personal experiences.
Modifications of any kind to a group member’s vehicle are by and for the benefit of that member but are encouraged to be shared with the group. Someone electing to perform similar or duplicate modifications to their vehicle are doing so at their own risk.