Oil is black & watery

[EloManga]

Hey, we've got this 4hp B&S mower that we found and the oil looks watery and is black. I've changed the oil 3 times and it goes black right away like a diesel, yet, it runs like a champ. I'm using straight 30 oil in it.
I asked a couple of guys at work and they said put thicker oil in it, but most likely the walls are scored and I'm getting blow by? It only puffs out blue on start up.
Would you guys agree to this or does anyone else have an idea on this?
Thanks

 

[Quest]

Do you smell a strong smell of gas (which means that your B&S is running extremely rich or serious cylinder washdown happening)?

Also: you can perform a compression check (engine warmed up) and see if you get proper compression.

If engine is determined to be defective (scoured cylinder walls, very likely in severely neglected B&S), try finding a used one to replace instead of rebuilding it.

Q.

 

[Tom_T]

If your clyinder is scored up or the rings are shot you'd be burning oil as well as the blow by. The breather on the crankcase would be misting out oil. Is this the case? How does the plug read? Does the old oil have a gas smell?

I know these are more questions than answers but it may just be a buildup of sludge that is cleaning itself out. I'd stick with the 30 weight for now.

 

[EloManga]

I don't have a compression tester, but I guess I could try to find one and see.
There is a slight oil burn, though I find that in all lawnmowers.
No oil misting out. The plug, I think it was blackish, I cleaned and regapped it last year, with gasoline. I'll check the oil for smell and get back to you. I had my neighbour have a look at it, we took the whole thing apart. Cleaned the carb, he sprayed the inside of the engine with some cleaner, made the oil milky, then after that, it runs fine, just the oil keeps going black.

 

[Tom_T]

Just run it with no worries.

 

[Bill Kapaun]

Originally Posted By: Tom_T
Just run it with no worries.


Ditto.
The engine probably wasn't maintained well and you have "ggop" in the crankcase.
You said you found it, so just run it.
Maybe change the oil 2X a year instead of once.

 

[EloManga]

I talked to a mechanic I know. He said that if the oil is going black, the crankcase could have sludge in it, making the oil black. He says try crankcase cleaner. What about doing a kerosene flush or even adding transmission fluid to it?

 

[pickled]

Just run shorter drains with some cheap 15W40 diesel oil (Rotella or Delo). Run a few hours and drain, run a few hours and drain...after about 3 of these you should be back to a cleaner version of what you started with. Good luck!

 

[Rock_Hudstone]

Originally Posted By: EloZE'PGT
I had my neighbour have a look at it, we took the whole thing apart. Cleaned the carb, he sprayed the inside of the engine with some cleaner, made the oil milky, then after that, it runs fine, just the oil keeps going black.

Keep the neighbor far away from your mower.
As you suspected, the piston rings are probably worn, the blue smoke and blackend oil is from blow-by, spraying solvent in the crankcase won't fix that.

You'll need to change the oil frequently. Also, clean and/or replace the spark plug often, it will foul quickly under those conditions.

I use Shell Rotella heavy-duty 30 wt. diesel motor oil, it has high levels of detergents and dispersants to better handle fuel diluted oil.

 

[Craig in Canada]

You could also try a straight weight SAE40, just to see if any of your conditions improve with a bit higher viscosity.

 

[Bror Jace]

Keep changing the oil ... 15W-40 my preferred weight but straight 40 will work in warm weather if the 15W-40 seems to get too runny too quickly. DO NOT put any more solvents of any kind in the crankcase as that will make any cylinder scoring or ring wear problem worse.

Also, use a top oil like MMO, Lucas UCL or some 2-stroke oil in the gas. I have seen this decrease oil consumption and it may even help keep gas out of your crankcase if it helps the rings seal better.

If your 'helpful' neighbor insists on helping you maintain your outdoor power equipment, suggest he give your wheel barrow a quick oil change.

 

[artificialist]

Valvoline Maxlife also contains a higher concentration of cleaning agents than regular motor oil.

 

[EloManga]

No no, he hasn't touched it since. I was only the first time, and he sprayed the stuff in the spark plug hole, making the oil white, but still watery. I changed it right after I saw that.
I'll re-clean the plug, and change the oil. I do have some Maxlife left, I could try that.
As for the diesel oil, is MM diesel oil ok to use also?

 

[Bror Jace]

"As for the diesel oil, is MM diesel oil OK to use also?"

I've never heard of it. Did you mean Wal-Mart? Yes, it would probably be fine in this application.

 

[EloManga]

Motomaster, from Canadian Tire. Same thing, so I guess "yes" is the answer.