What oil to use for B&S Quantum with issues?

[bakechad]

I currently have a Troy-Bilt push mower with a 6.5hp B&S Quantum that I run about 40 hours per year. I started seeing minor issues after my third oil change and I am trying to decide what oil I should use for my next change. I have been debating between 30w dino and Amsoil Formula 4-Stroke 10W-30/SAE 30 Small Engine Oil.

Here is my engine history:

Purchased Oct. 2004

First oil change (Shell Dino 30W), new plug, new air filter – April 2005

Second oil change (M1 5w-30), new plug, and new air filter – April 2006

Third oil change (M1/PP 5w-30 mix), new plug, and new air filter – April 2007
(Engine now blows a single puff of smoke at start-up)

Fourth oil change (PP 5w-30w), new plug, and new air filter – April 2008
(Old plug had oil on it and engine still blows single puff of smoke at startup)

I read a post about a guy that switched his B&S engine to Mobil 1 and started blowing smoke at start-up. I wonder if oil is playing a roll in the smoke and plug condition or if I just have engine issues.

 

[Jim 5]

I don't know what it is, but I have a number of 1-2 year old gas engines that blow a puff of smoke on start up. These are good engines (including an expensive kawasaki) with no problems.

I wouldn't worry about it at all. Your engine has been better maintained than probably 90% of the mowers on the planet.

 

[Mkos1980]

I have a Craftsman with the 6.5HP unit and with just a tad over 2K hours, I'm still using M1 5w-30 which is the new specifications that [censored] ask for. The engine was used commercially for 3 years then the mower went but motor was still good. I swapped it onto a new deck. No smoke no nothing.

 

[Boomer]

I have a 22 year old grinder with a 5HP B&S engine. Have run it on Valvoline and PZ 5W-30 all those years. Safter 3 years or so, gave the puff of smoke. But still runs like a champ and grinds just fine. Probably gets an average of 15 hours use a year under some heavy loads.

 

[RWEST]

A little smoke on startup with anything except a straight 30 weight (I use Shell Rotella T)has been a common occurrence with B&S engines, in my experience. I've used quite a few mowers and such with B&S engines over the years, and they all seem to act that way. Dunno why, but I doubt it's hurting anything.

If you really wanna see a smokescreen, you should see my 25 HP Kohler twin after it's been run for a while, then restarted after sitting for a bit on any kind of sidehill slope. No mosquitos for a 5 mile radius!!

 

[Bill Kapaun]

A bit of smoke at start up is a non issue, ESPECIALLY on a vertical engine.
Slightly overfilling the oil or storing with the cylinder slightly down exacerbates the problem.

Why 5W instead of 10W?