Prolly getting a little oil drainback from one of the valve guides or mebbe the piston oil control ring is sticking a little.
If the engine is not burning a lot of oil on the dipstick (check that every time you fire it up), I would leave well enuff alone and just try to have tractor sitting where startup amoke con blow outside during startup/warmup...

whitish smoke = oil; blackish smoke = fuel.

All the aluminum briggs i've had only do this when it's winter. I guess it's the kool bore design

A-C: I agree with rcbe , since no or negligible Oil consumption is identified the Smoke is very likely due to worn valve guides in conjunction with less than pliable valve seals in cooler temps. I would also say just leave it for now or at least till your next oil change then add a conditioner or Oil for Older High Milage Engines ..Ty .

it had SAE 30 with marvel mystery oil mixed in and I changed it to 10W-30 with marvel mixed in. It also has marvel in the gas.

Too much Marvel in the oil, and the oil should never be 10W-30!! Those engines were not designed for the multi-viscosity oils!
try straight 30W oil in it. might surprise you.
Of course, there are some here in this forum who will tell me i'm just old fashioned, and i suppose i might be, but the preceding i learned from the educated heads who write in this forum!

Hey Rusty I'am Old School Too , but just learned recently that Honda currently recommends Multi 10W-40W on their Mowers..go figure ! I still believe sae-30 most applications , but who am I to argue with Japanese Engineers lol .

Note: Question Marvel Products , I asked previously and have not been given any feedback , do they supply Oil and Gas Treatment Products both or do you utilize same product for both treatments ?

There is just the one MMM product (so far as I have ever known). I suggest that the ratio for adding MMM to the gas tank be followed, too much is not providing more protection. MMM in the crankcase lube oil is up to the owner, I doubt MMM in the lube oil improves much of anything, considering the design details and specs of modern oils. Adding a "bit of oil" to the fuel however, does provide some benefits and "close some gaps" that the gasoline marketeers omit (my opinion). I also believe that adding a bit of the new, synthetic "2 stroke fuel mix oil" to the fuel tank might turn out to be better than MMM (but you would definitely use less than if mixing a gallon to burn in a stroke engine).

The owners manual for the tractor says 10W-30 all year round

I run synthetic 10W-30 year round in my Simplicity 728 with no problems. 8hp with a newer shortblock (I/C). Would synthetic in the 6hp be better?

Years ago I was commuting 150 miles per day, using a VW Fox, with a 4 cylinder fuel injected engine. I was really racking up the miles, & the engine got pretty noisy at 200,000 miles or so. One summer, I found some 50 weight oil, nondetergent, at an auto parts store. When I ran this in the Fox, it was noticeably quieter. I only ran the 50 weight June, July, and August. But it sure seemed to help an old engine keep running in hot weather. Eventually the undercarriage and other parts exposed to road salt corroded past the point of no return, & I got rid of the car. But the engine ran fine 'till the end.

Mownie: Thanks Bro for the follow up Reply ! I have never heard of the MMO Product until this Site lol , but I have heard some good things but was getting confused. I have began using Lucas Products within the last few Yrs, and have had great success (Power Steering , Top End , Fuel Cleaner Lubricant) Etc.

AC: I have no idea where you are Geographically Located , but I love Synthetics , but you must use some common sense , they are more expensive but do a much better job of carbon contamination protection and viscosity break down protection. Also if you are in a climate with severe thermal swings (Hot to Cold) again Syntehtics by design work very well .

Eric: Have been to Milwaukee numerous times not to far from the Great White North , but in the summer , yep it gets Hot , been there with my Harley at County Stadium in the 80's 100 F...Yep 50 Weight would work fine in those Temps , especially with a slightly less than Fresh Engine lol . :)

Western WI. It's 4 degrees right now. I love synthetics too that's why i was thinking about trying it in the 6hp on this allis