Part of the problem with these Estate Keepers is the engine is crammed in the back of the tractor and there is not a lot of room to work on them like with other tractors. The oil drain plug can be tricky to find on these if you're not familiar with them. Other Wisconsin engines installed on Bolens tractors have the oil drain plug on the side of the case. However, if it was located in the same place on the Estate Keepers, it would be inaccessible to drain the oil unless you pulled the whole engine out of the tractor! Thankfully, Bolens had thought of that and they requested that Wisconsin design them with the oil drain plug in a different location to make them easier to access. However, it is still not entirely CONVENIENT for your average owner to change the oil on these, which I think led many of these to have had the oil changed very infrequently, if at all.
I ended up using a jack to lift the back of my tractor to access the oil drain plug, but others might rather use a pair of automotive ramps that they could back the tractor up onto to get access to the drain plug instead. Whatever method you use, you have to get under the back end of the tractor. I preferred using a jack since once I pulled the drain plug out, I was able to lower the jack to be sure I got as much of the old oil out of the engine as possible.
Here are some shots of the tractor jacked up in my garage:
Next, once you crawl under the back of the tractor after it is jacked up, you will see the oil drain plug on the bottom of the engine. It is located at the bottom of the engine's rear crankcase cover, near where the lower PTO drive pulleys are on the tractor. You can see it in the picture below (where the arrow is pointing):
Before I started draining the oil, I pulled the dipstick to check the condition of the oil, which was pretty dark and sludgey if I do say so myself. It definitely was LONG overdue to be changed:
Next, I got out my allen bits set (I believe this was either a 1/4" or 5/16" allen bit), put the bit on my socket adapter, and used a LONG extension on my socket wrench to take the plug out. (Just be sure to have your oil drain pan in place before you pull the plug out as oil will go everywhere.) Also, a magnetic bit driver would be useful so you don't drop or lose the plug. I was careful when removing mine that I didn't drop it in the oil drain pan.
I also swapped out oil drain pans when the initial flow of oil slowed down and used a cut-off Gatorade bottle to put there to collect the rest of the oil from the engine. This allowed me to slowly lower the jack all the way until the tractor was down on the ground to try to get all of the used oil out of the engine. (Notice that the rear wheels are on the ground in this picture):
Here are some photos of the old oil that came out of my engine. YUCK!! I'm so glad I changed it, but I only wish I did it earlier than I did.
Now it's time to add in some fresh oil. (Wait, aren't we forgetting something? Oh, of course, be sure you put the drain plug back in FIRST before filling your engine up with new oil!) I ended up using Valvoline conventional 30W oil in my engine, since this is what the manufacturer calls for. I also added in between 1/8 and 1/4 of a bottle of STP Oil Treatment with the oil. STP contains ZDDP, which is a zinc anti-wear additive that is good to use in these older engines. (The old motor oil available in the '60s and '70s used to contain more Zinc than today's blends.)
Now, honestly I think I may have overfilled my engine with oil, especially since I added the STP treatment. I put in a little over a quart of oil and as you can see by the level on the dipstick, it is a little over the operating range. I would have figured this engine would take more than just one quart of oil to fill it up, but I guess not. (You can tell I was playing it safe since I bought two quarts of oil plus the STP treatment to put into the engine...) My dipstick is also probably a bit inaccurate though since the top is broken on it and the dipstick goes into the tube a lot farther than it should, probably. Still, so long as I have oil appearing on the dipstick and it looks fresh, I'm happy with that!
So, that is really about all there is to it! I mowed my lawn with this tractor again a couple of weeks after changing the oil and it ran well and I'm sure she was a lot happier being run with fresh oil in her! (Yes, I know it took me THAT LONG to post pictures of the oil change that I did on this tractor at the end of June...)
Hopefully after seeing how easy it was to change the oil on my tractor (it took me maybe a half an hour to an hour at most and that included taking all of the photos...), this will give you the confidence to tackle changing the oil on your tractor!