As far as I know the Jet engines are a modern-type (circa 1953) engine, and any modern oil should work. If the engine has not been overhauled in a long time, there are those who feel that a non-detergent oil should be used, because (it is felt) a detergent oil would loosen all the sludge in the engine and start to circulate it. In which case some of it could block smaller oil passages, leading to engine failure. However, there are others who say this is not true. So, go figure!

If you've acquired a Jet whose engine condition is unknown, it wouldn't be a bad idea drain the oil, remove the oil pan, and clean it out (and clean out the gunk within the engine as well) so you're starting out on the right foot with your new oil.

There is no real need to remove the sump from a Jet Motor, as the oil pick up floats and takes the oil from the top rather than from the bottom as in the earlier splash fed motors. Any good modern oil is usable in a Jet, but depending on the mileage and your climate whether you use a 15W-40 or a 20W-50. I have always used Havoline 20W-20 or Castrol GTX in my Jet, which I have now driven for 43 years.
Geoff

Thats all well and good Geoff ,but what if we want long life out of the motor ? 😛
Roger

I can't answer that. Check with me when I've been driving it for 60 years and I'll let you know if it worked! I'll only be 93 then. :whistle:

Thank you, Jon and Geoff, for the responses. As usual Geoff-please add to my seemingly endless invoice! I sure hope I can ask you about my Essex and Jet when you make it to 93...

Joe

Geoff , thats an good point about the floating pickup missing all the crud
Roger