Don't be embarrassed about not using fabric softener Cookiemonster! Apparently it is no good for your machine. Vinegar is the way to go
FYI I accidently washed some of DH's gearbox oil soaked clothes and it made my machine stink. I filled it up with just hot water and bleach and left it to soak over night. then i emptied it and did an empty hot wash with bi-carb and vinegar and it was 'good as new'.