You might do a search using stain removal as the words you are searching for. There has been a lot of discussion on this topic in other areas of this forum.
I have had success in removing stains from the ceiling by mixing 1/3rd bleach with 2/3rds water. Shake it up and using a small sprayer, spray the stain lightly (don't soak it) and then let air dry (don't blot it). This removed the stain for me. I have the "off white color ceiling in my MH. Just don't soak it or blot it. I did have to air out the coach for the day afterwards to get rid of the bleach smell which you will have after the treatment. Others will have other suggestions and what to use.
Hope this helps.
Dave and Karen -- '02 Ultimate Advantage 36 C, 350 HP Cummins, Allison 3060 Tranny
'13 Ford Edge, InvisiBrake