Oil

[Chris Kewley]

Hello all

Does anybody out there have a opinion on using motor oil/trans fluid in Welch 1399-1405 pumps. I know the rubber seals will swell but outside of that is there any adverse affects?
I should also point out that these pumps are used in labs & are constantly being contaminated, so oil changes are quite frequent.

[verdatum]

Based on what I've read, motor oil is going to negatively effect your ultimate vacuum pressure and slow your pumpdown times.  It has a higher vapor pressure, which will contribute to more backstreaming into the chamber.  For reasons of flammability, there are certain chemicals you'd never want to pump with motor oil (don't ask me what, I only ever pump air), although other hydrocarbon based pump-oils have this same issue.  I can only assume that transmission fluid would have the same issues.

[macona]

Dont do it. All sorts of stuff in the oil you do not want.