51 M Gas in engine oil?

I have a 51 M and I have noticed that the engine oil is more of a dark gray color and seems to have a gas odor to it. Any idea what may be causing this? With the carb arrangement on that tractor, it doesn't seem likely that a leaky needle valve would allow gas to travel vertically into the cylinders. I have checked the coolant level several times and it does not appear to be using any. Tractor runs very well otherwise.

I have noticed that there will be a oily black residue that appears to leak from the exhaust manifold gasket after the tractor has been running for a while. I was told that it is a condensate that forms and is nothing to worry about. I just added this in case it may be relevant. Let me know what you think!

The only way for gas to get into the cylinders and therefore the oil is through the carb. A full fuel tank should have the gas level above the top of the manifold. Then there is the matter if the tractor is parked facing down hill which would aid fuel movement. The carb needle valve for the fuel bowl is not closing is my guess. I've got a M so I will check my theory in a little while.

Gas will not turn oil gray but water will sounds like you might have a bad head gasket or condensation from setting

Gas tank is higher than engine so leaking
needle valve will allow gas to enter engine.
Shut off valve at tank.
You could also have moisture in crankcase.

It can be a leaky carburetor, or a lot of short runs where engine did not warm up and boil excess fuel from starting out.

Yes your needle and seat is leaking or the float is bad. The sintered bronze weep plug in the bottom of the carb is also plugged. The oily residue is gas thinned oil getting past the rings and valve seals and getting into the combustion chamber. Yes the grey is most likely condensate.

What happens is the gas leaking past the needle builds up in the carb throat and air hose. When you pull the starter all that gas gets sucked into the engine where a lot of it bypasses the rings and ends up in the oil pan. I have seen rods bent from the pistons trying to compress that liquid gas.

You need to put a kit in the carb. Make sure the float isn't bad. Order a new bronze weep plug from roberts and replace your clogged one. Pin punches makes it easy. With that new plug it won't matter if it does leak - you'll see it dripping on to the ground and there is NO chance of gas buildup. That weep plug is one of the most important parts in a TSX carb and no one bothers to change it.

Change the engine oil and filter as well as the breather oil. Clean your oil cap mesh so it can breathe. Keep a check on the TOM oil level to be sure it isn't leaking into the engine as well.

Gas in oil is caused by a float needle not seating 100% and yes gas can go up due to if turning to a vapor and then condensing. That is why one should shut the gas off at the sediment bowl when not using it. I once worked on a Ford 9N that I drained 5 gallons of oil/gas out of the oil pan because the guy did not shut off the gas when he parked it

I believe this thread may have answered a perplexing problem for me. I recently acquired a JD 1020 from out of state. I drove it before buying, and all seemed OK (a little breather smoke, but no obvious problems). I had it trucked to my home, and when I started it up the little grasshopper smoked like a steel factory through the exhaust! I checked the oil level, which was normal when I bought it, and it seemed way overfilled. I wrote it off as having misread it when I inspected it prior to purchase.
As of now it has stopped smoking through the exhaust, and the oil level is about normal. I'm thinking that, while being trucked about 500 miles, that its likely the carb valve stuck or bounced open and drained a bunch of gas into the oil.
I guess that means I'd better change the oil pretty quick....