B&S burning oil

[GMFan]

My family owns a 1997 Lawnboy mower with a commercial grade 6hp B&S engine on it. I'll admit that the oil was not changed every season, and sometimes in its younger days it may have gone 3 years with no oil changes (I was younger at the time and didn't know any better). However, we typically mow 15hrs a season so that's not too bad.

Anyway, I've been personally changing the oil consistently for the past few years now every season. Last year I did a Frankenstein mix of Mobil Clean/Pennzoil/Castrol 10w40. It would smoke a little bit on start up so I switched to HD 30.

I put Castrol HD 30W in it this time, and it still smokes a little on start up for about 5 seconds...it blows black smoke out of the exhaust.

Is this something to be concerned about, or could it possibly be the residual multigrade 10w40 in there getting burned out?

Thanks.

 

[bepperb]

Do you prime or choke it? Black smoke is more likely rich combustion than oil burning.

But anyway, it's not something to be concerned about.

 

[Hitzy]

Have you changed the plugs or cleaned/changed the air filter?

 

[GMFan]

The air filter is cleaned and re-oiled every year with the oil change. Plug was changed a year ago (I do the plug every other year).

 

[greenaccord02]

A carb cleaning and tune wouldn't hurt, but then neither does the smoke, so I wouldn't sweat it unless you get bored and want to take apart a lawnmower's carb. Also, this could be leaking valves, in which case you really don't want to deal with it and it doesn't matter anyway.

 

[dwendt44]

You could try a fill of high mileage 10W-40 and see if things improve.
HM oils contain seal conditioners and may help the valve seals.

 

[rainman49]

I'd try a double dose of Seafoam in the gas before I did anything else. Like bepperb said, black smoke is a sign of a rich condition. Before I got my ZTR, I had a lawn tractor with a 15hp Kohler that was running bad, belching a little dark smoke. A tank dosed with Seafoam (I used twice the recommended amount) soon returned it to the smooth running motor to which I was accustomed. BTW, I gave that mower to my brother three years ago and it's still running like a champ.

 

[nooil]

I use a 15w-40 HDEO in mine

 

[StevieC]

If it's running too rich this could be why it's burning oil as it's washing the cylinder walls... I would take the Carb apart, thoroughly clean it and replace any worn parts/seals etc. and reassemble.

Then setup the fuel mixture if it's an older style and you should be good to go!

If it still burns oil, then switch to a heavier weight...