1928 six speed oil

I have just aquired a 1928 six speed with Waukesha XA 222D 4 cyl motor. Where is the point on motor where oil is checked and what is the oil capacity of this motor? Thanks, Mike

In the manual it says 4 quarts. I just changed the oil in my 28 six speed special. I used 15-40 oil.

Thanks SS for the oil capacity. I have not been able to find the "dip stick" or whatever mechanism this motor has for checking oil. There is a grey colored knob just behind starter and appears this would access a dipstick. Have not been able to remove and afraid to pull too hard on this knob. This is on passenger side of block. Any info greatly appreciated.

Yes that grey thing is the dipstick. The knob business is made of pot metal and they crack and expand making them very difficult to remove. Be careful and you may get it. Somebody ground 2 flat sides on mine so you can use a vise grip if necessary.