How Far Can You "Stretch" (Dilute) Ilford Multigrade Developer?

So I'm trying for the first time, Ilford Multi-Grade Developer at 1:14. Second time around did a 1:19 and got the same acceptable results.
So, perhaps maybe, say, 1:22 - 23, or is it too "thinned out" by then? I don't mind waiting - agitating for 2-3 minutes.
My prints are 8 X 10's.

It is sort of like asking how far you can drive your car on bald tires. You are going to get a lot of different answers. My advice is that you set up one tray with a 1:9 dilution and one with 1:23 dilution, expose two sheets of paper from your favorite negative, process them, note the developing time and any differences in the prints, and choose which one you like best.

I teach high school photography. For economy, we dilute Ilford MG to 1+14. Ilford MG IV Pearl gets a minute in the developer. Looks great. I've thought about increasing the dilution, but that would probably increase development time. I cannot have kids standing around the tray waiting for their turn.

Your results may also vary with the type of paper.
If you tend to use up (exhaust) the developer during each session, it will probably result in false economy, because you will be more likely to have to discard and replace your developer mid-session.

I'm sure you'll be able to dilute it up to 1+22 without issue. Keep the stock developer amount the same. To compensate for exhaustion, you could always employ factorial development.

I don't do large dilutions bit if I did I would pay close attention to capacity issues. when XTOL film developer first came out they had a pamphlet ( really a 8x10 booklet ) that had all sorts of extreme dilutions and it caused all sorts of problems ( some suggest running out of developing agent was one of the causes of XSDS but no one is quite sure ) so another test in addition to the one suggested above might be run a bunch of 4x5 prints through your extreme dilution with the lights on 1 after the other and see how long it takes to turn the paper black AND when it stops turning the paper black.
have fun !
John

A higher dilution contains less of the developing agents and will exhaust faster. ; i.e., fewer prints per liter. If you only develop a few prints and then toss otherwise good developer at the end of the session, then a higher dilution may be more economical. Side effect: development time may be extended with higher dilutions.

At some point, a solution will become too diluted to work effectively; the concentration of developing agents isn't great enough to initiate and sustain development. Most developers need an alkaline environment to work well and extreme dilution will change the pH toward neutral at some point, even with buffered developers.

Before complete failure due to extreme dilution, areas of greater density will suffer due to lack of development (the theory behind many compensating developers).

How far you can go with dilution depends on your patience and the results you require.

Doremus