High again a-c , since your in Wisconsin , you will see some severe (cold) winter weather all most same as up North here.
If you have a heated garage and electric start 10W-40 would be okay for winter usage . I would be more inclined top go with the 10W-30 for Winter in a regular Mineral Oil Grade .
When you get into Synthetics Amsoil is the Best Product Going . I use 25-50 Multi Grade Synthetic Amsoil in all my current Generators and my Neighbor does the same on his new Cub Cadet Lawn Tractor that has a Snow-blower attachment for Winter . Some Old Time Mechanics frown on synthetic Oil on Older Engines , I agree within reason that is why I use Regular 15W-40 Rotella in my F-250 Diesel and not Synthetic Blend since it has over 200,00 Mikes and dont burnt a drop yet !

I had an old '75 Ford van with 150K miles on the engine, in perfect running condition, when I switched to Amsoil. Within a week, the oil pressure went to zero at idle (knocked badly) and took a good city block to bring it up to 40#.

Despite Amsoil's claims, I would never use it in an old engine. It cleans up the sludge and ruins the bearings at the same time.

It had a 351W engine and I drove the van for a few months until I could find another 351 at a junkyard. They were rare as hen's teeth in the '90s. Even with the knock, the engine still went another few months.

It would be in an unheated barn and it is a pull start. Like I said I don't plan on using it below zero.

a/c: Upon further reading your initial note , you have a New B&S ! I would most definitely go with Amsoil Synthetic for Air Cooled Motors. You will never look back ... I have just introduced it (last fall) into my 3 yr old B&S Quantum XTE runs smoother with noticeably more power !
Bay: I agree 100% with you analogy on the 351 Windsor . I had a friend who actually put Valvoline Durablend (60/40) Synthetic into his Old Delco Unit which was burning Oil and turned the bottom end bearing out of it within 1/2 hr running time of the oil change. I on the other hand used it along with Religious Purolator Filters within my 5 litre Eddie Bauer F-150 for over 120,000 Miles when most 5 litre of its Vintage (1991) where blowing rods before 100,000 Miles . I have numerous Buddies who have over 100,000 Miles on their Harley's Running Amsoil ...Great Oil but not available everywhere and it is more expensive ...Take it for what it's Worth ! Not all Engines are the Same !

My current 5L '93 ford van has over 150K on it. It has used Syntec full synthetic oil from new. I am now switching over to Mobil 1 as I hear that Syntec is not a true synthetic.

The 5L engines are legendary, sometimes going 500K or more with no problems.

Mobil 1 is the correct choice.

I tried Mobil 1 10W-30 and it went through it like water. in summer with lows in the 70's and highs in the 90's with SAE 30 it uses 1/16 of an inch every week if under heavy load and none if under normal load. With convetional 10W-30 it uses 1/16th of an inch every 4 days under normal load. With Mobil 1 10W-30 It used 3/8 of an inch in 2 hours. Im sticking with tried and true petrolium oil.

a/c 25/50 and you would be burning none ! That is why all the New Air Cooled Generator Manufacturers are recommending same within numerous operating manuals. Sooner or later your oil consumption may cause you a top end repair bill . Keep a eye on your spark plug colour , Sae-30 1/16th under high ambient temps and severe loading conditions is actually not bad . The Winter usage was your original question and 30 weight in Wisc. may be a problem without heated garage lol .

My 10 yr old JD325 with a Kawasaki 18HP AC engine has over 400 hrs on it. I used 10W-30 conventional oil for the first 50 hours, then switched to Mobil 1, 10W-30. I change the oil and filter once a year which is about 50hrs. It has never used oil, and runs great. When I first bought the tractor, the "Old Time Dealer" suggested only using SAE 30, and no synthetic. After reading posts from many users of Mobil 1, I decided to go with synthetic because of the wide temperature ranges of an air cooled engine. I still think it was a good choice.
Charles Ranheim

The spark plug color is tan. No oil on the plug. Under normal load it uses no oil. Chilton small engine repair states in the Briggs section "In hot weather, when under heavy load, or when brand new engines may consume oil at a rate which requires the crankcase to be refilled several time between oil changes" I know its info from the 60's but thought I'd put it out there.

a/c: Tan to medium Brown is Optimum Fuel / Air Mixture Plug Colouration . Chilton off the cuff advice is correct. But they also recommend follow up decarbonizing of the heads , Pistons c/w wing ring cleaning etc. If you read along further lol . That is because 1960's Oil Technology along with Compression Ratio's where far different then today , even within Small Air Cooled Engine Design. I agree that a Water Cooled 427 Big Block burning a quart of oil every 1000 Miles was a Good Thing . But not the Same with a Air Cooled High Revving 4-Cycle Lawnmower or a Highly Loaded Mower in Deep Wet Grass . If you insist on Sae 30 Oil Get the Best . Be religious with the Oil Change Frequency , Since Mineral Based Oils hate Carbon fouling and leads to viscosity breakdown and all kinds of other nasty stuff around valves ...etc. As said you engine appears to have good sealability since your consumption rate is within spec . But you will have to think about the Winter Oil Selection without Temps at or above freezing and Cold Storage to Boot :)

It sounds to me as if you are having some problems getting an accurate reading from the dipstick. Synthetic clings longer in an engine and takes much more time to return to the sump.

In this one I run Citgo SAE 30 with alittle SeaFoam in the oil. I can find the 48oz jug of Briggs branded SAE 30 for $6. I was thinking of switching to that.

If you ran SeaFoam in the oil, you have most likely damaged your engine.

Sea Foam claims that it can be added to oil.

I think anything that's sludged or just plain dirty internal surfaces, with no oil filter, is a bad choice for synthetics. Unless, of course, you know exactly what you're doing.

I've used SeaFoam in the oil everything from This 8hp Briggs to the 152 4 cylinder in my Farmall Super H with no problems. Helps clean the gunk out of them and keeps the rings from sticking

SeaFoam is a solvent that dilutes and destroye the lubricative properties of engine oil. No wonder you're having engine problems.

Star: Seafoam or any Oil Conditioner Cleaner will not harm your engine if used in moderation . Even small amount of transmission fluid will clean up valve carbon issues or sticking rings. Normally only req'd on older engines .

Bay: Your correct within the 5-litre design before mid 90 after mid 1991 , most late 1990- early 91 had both rod bearing related and piston related failures (ring/piston expansion rate issues) around the 90K Mile Mark . It was Quality Control Issues that Ford had Recall Bulletin Status on . As I said my ran ok for over 120,000 with routine use of Valvoline Semi-Synthetic Durablend.

a/c: Let us know how you make out Bro !

"Star: Seafoam or any Oil Conditioner Cleaner will not harm your engine if used in moderation . Even small amount of transmission fluid will clean up valve carbon issues or sticking rings. Normally only req'd on older engines"

SeaFoam is a good cleaner for old engines that have been neglected, but so is plain naphtha. If you desire to spend your money on overpriced chemical cleaners, then have at it. If you use a good quality synthetic in the engine and change it on a regular basis then you donÂt have to worry about using an engine cleaner. Using SeaFoam in the oil for "normal" use is foolish. Walmart shelves are burdened with many oil additives and all of them are snakeoil.

Star: Your Preaching to The Choir Dude ! Yep Napha work for an intended solution to a problem .

Note: I'am a Strong Supporter of Full Synthetic Oils have been since 1976 . Do believe that some older engines do not react well to these light viscosity multi blends . therefore caution is needed when engine oil change is considered. As for snake oils , some yes others within fuel conditioner lubricant / cleaners such as Lucas and Duralube sorry no snake oil I have witnessed their effective results within injectors on Gas And Diesel Applications over the yrs .

I am in Wisconsin and use 5-20 Durablend in my SB.Unheated garage and pull start.Have never used the electric start and it starts within 3 pulls.Uses no oil.

Gopher: Well there you go another Satisfied Semi-synthetic Oil Customer ! I have very good results with my Valvoline usage of Durablend also . Rotella now in my Diesel but would opt to Full Synthetic Rotella - T in my next New Diesel without a Doubt !

The rule that I go by in the repair bus. for 30 years. If ya use conventional oil stay with it . I recomend only synthetic on a new motor... People would want sythetic in a car with 90000 miles on it , we tried it and the thing would use oil. I use synthetic in 6 motors and never had a issue , I feel the xtra cost is worth it. My new compressor states synthetic for continuous run time and second is conventional. Everything is dollars and cents , a lot of people do not believe in synthetic .

'Everything is dollars and cents , a lot of people do not believe in synthetic ."

Yup, I use syn. because it is cheaper in the long run given the cost of today's dino oil AND I don't like to get out and change oil when it is zero.

Walt Conner

Walt: I think your right $ puts off a lot of people .

I have used synthetic for 30 years or more ,the Germans used it in WW2 . I had a lot of customers who would put it in a car and think ,ok now we wont change the oil , wrong . You would have to educate them on regular change intervals. Do I think synthetic last longer yes ,is it better than conventional, yes. Do people want to pay extra for it , thats up to them.