Will a rubber O ring work in place of a plastic O ring?

In what? A Distributor? Fuel Injector? Air-Conditioning Piping? House Plumbing? A garden hose...? Rainbow loom bands...?

Distributor

Distributor

Assuming its a V6.. No, it uses a specific rubber type. A rigid plastic one will not be a suitable replacement.
Costs less than $10 from a dealer and probably similar from a Repco or alike, at that price why would you want to chance it with something else isn't designed for the specific purpose?

It is a ridged plastic one. no auto shop stocks it here

Mitsubishi have them, they are a specific size

It may have come out with the appearance of rigid plastic.. but if it is the one at the end of the V6 distributor, going into the head, it started life as a soft rubber one.
Heat cycles will harden rubber seals and o-rings with time and kilometres under their belt.

Ok. This one is as solid as a rock. Out of a 03 TJ. Now that I have it out I can go see with the mitsubishi dealer in Kalgoorlie but dont recon they will have it in stock

Is solid because it has gone hard. They can always order this in MD619990

Oh and Kalgoorlie is a long long way from Tasmania

I recently done mine, could not believe the amount of oil splashed all over the transfer case.

I recently done mine, could not believe the amount of oil splashed all over the transfer case.

How hard was it to get back in?

Hi ya,,better late than never for a response....I did mine on the weekend..getting the distributor out of the head was the time consuming part..didnt want to come out, though a bit of gentle tappting from underneath did it...getting it back in was so much easier.

FYI - the o-ring cost me $11 from Mitsubishi dealer (Part number MD619990). I did find that Bursons sell them in packs of 3 for $17. (They don't sell separately), so if you know of others wanting to do the o-ring, Bursons they way to go and share the cost.

bursons geelong sold me 1 $10