Briggs Stratton oil

Friend just bought a new Snapper 0turn mower with 25 hp B & S engine i was surprised to learn they recommend straight grade 30 wt oil in it.
Didn't Know they recommend a straight wt oil in anything any more.

I have a Simplicity with a 20 HP Briggs engine that is 10 years old. They recommended 30 Wt then too and that's all I have used with no problem.
DWF

The 30wt oils is for summer use. That is 70?f weather. 5w20 or 10w30 is for winter use.

I use straight 30w in my older mowers. It was difficult to find in gallon size. Autozone didn't have any in gallon size, and they looked it up and said they couldn't even order a gallon. Was 4.99 a quart, and I needed several. Found a gallon of 30w Rotella at Wallyworld for $14.99.

The oil in an air cooled engine can reach over 300 deg F in normal operating conditions. Oil in liquid cooled engines is in the low 200 deg F range in normal conditions. This according to a technical paper on small engine oil published by Amsoil. Over at the "Bob is the Oil Guy" site somebody shot an oil filter external temperature with an infrared thermometer and measured 350 deg F after a difficult mowing job during hot weather. Seems like the oil sold by Briggs and Stratton and also generic brand small engine oil sold in stores is 30w. I find that most all small engine oil requirements call for 10W 30 in winter conditions. I own and operate a wide variety of new and older small engines. I have used both multi viscosity and 30W oil over the years and have never had an oil related failure. Having said that, small engines air cooled engines can be harder on oil than a large diesel or gasoline liquid cooled engine. I have reduced oil consumption in several older air cooled engines by running 30w compared to multi viscosity oil. Koehler and B&S have both stated this fact in their operators manuals over many years. Amsoil now has a small engine synthetic oil that achieves both a 30w and a 10w-30 rating without the use of viscosity modifiers. This means that the viscosity will not degrade under typical high oil operating temps, and the same oil could be used year around if necessary. If I had had this oil in my new B&S generator it probably would have saved me from snapping the pull starter rope when I tried to start it with 30w oil at -10 deg F last winter.

We bought a new JD zero turn with a Briggs 2 years ago and I thought they recommended 10-30. But I think either would be fine, it's not like your going to use a zero-turn in the winter!

I run 10w-30 full syn in all my air cooled engines and change once a year or maybe 2 years with little use. Some are new some older used for different chores around the place. I mow a lot of grass. As far as I see it, all the bla bla on air cooled engines running hotter and all is just that......bla bla. I have 2 non contact Infrared/laser thermometers both working fine and recording withing a few degrees of each other. I have over half a dozen 4 cycle air cooled machines with 5 of them (Honda 18, BS 18, 20, 22, and 26 Vanguard) being V twins on lawn mowers or utility vehicles..

Numerous times, on the hottest days here in N. TX., I measured all over the machines after a hard mowing and the max temp I found on the engine was the crankcase and it was 187F with the mufflers running between 550 and 600F. My 2011 Silverado 1500 4.8 V8 has 2 electric fans and the temp gauge sits rock solid at 210!!!!!!!!!!!!!!!!!!!!

Yes, And you should buy the 30w that is made for small engines.
Different additives in it for small engines I believe.
If you check your manual it may recommend a different weight for temps below 32 degrees.
NAPA and True Value sell 30w oil for small engines.

Some other small engines I own recommend 10w-30 all year like my Cub Cadet engine.
My Briggs two cylinder says 30w above 32 degrees and 5w-30 below 32 degrees. API-SL-SG
I have another Briggs on a generator that recommends 10w-30 all year.
I just put the oil in them that the manual list and in the last 50 years I have never blown an engine.
I guess they know what they are talking about.
You will probably get replies that will have just about every weight oil made so you decide what you want to do.

The good folks at Lycoming and Continental engines have done tons of research on air-cooled oil needs for many decades. Although some viscosity modifiers are ok in an air-cooled engine, there are plenty that are not good. They will eventually cause a shear-point breakdown due to overheat, and loss of effective lubrication.

Mobil Oil found this out the hard way when they introduce their 15W-40 aviation Mobil-1 oil product, and suffered several in-flight engine failures caused by oil failure. Several people died before Mobil withdrew it from the market, and the FAA banned it from use. Mobil also bought hundreds of aircraft engines which they damaged with the Mobil-1 product

It's not the base oil that is the issue, it's the additive package. The long chain molecules of the modifiers are not lubricants, but they have a temp coef that lends them well to altering the viscosity when cold. But - too hot is always a problem. What is saving the oil companies now is that the modern SG and SL oils are so much better than the first gen multivis oils. Also, the base stock dino oil is much superior to the stuff that was hydrocracked just 15-20 years ago.

Better base stocks, better type, and molecular bonding have made modern multi-vis oils safe for many air-cooled engines. Doesn't mean they are better for air cooled, just that they are so good, the flaws are not as noticeable.

I read all the answers so far and no one mentioned that 'flat tappet cams and followers' are still used on small engines. These engines NEED Zinc. Zinc is no longer put in regular motor oils as it can destroy the Catalytic Convertor. Small engines, up to and including the Harley Davidson motorcycle engines NEED that zinc. It can be purchased online; in stores? I don't know. I use the additive in my older 'fleet'.('68 Mustang with J-Code 302-never torn down except for valve jobs @ 40,000 and 80,000 miles due to incorrect Ford valve adjustment information) Now she's nearing 130,000 miles and still runs like the car I asked my girlfriend ( now wife of 43 years) to marry me. Yep, still together (I'm almost 70) and she's (so far) not disappointed with me.

Zinc my not be found in some oils it is still easy to find. Shell Rotella T , Lucas,Royal Purple and others still have Zinc. Lucas also makes a Zinc additive.

Since I have never verified the actual oil temperature on my small air cooled engines I thought it would be a good day to try it and see whether there is any substance to the idea of air-cooled engine oil running hotter than liquid cooled engines. It is 71 degrees here today and I measured the oil temp on my Jeep Cherokee engine after a 10 mile drive on the highway. It was running at 152 degrees F. I had some mowing to do which I used a wheel horse tractor with Onan p220g 20 horsepower engine. After 20 minutes of mowing the oil filter external temperature was 204 degrees F. Since it is a very mild day here I have seen enough evidence to be convinced that air cooled engine oil run significantly hotter than liquid cooled engines operated in the same environment. That is reason enough for me to run a different engine oil in my air cooled engines compared to liquid cooled. Everyone is going to have a different judgment on this but I believe it is worthwhile to make sure that your air-cooled engine oil is not running too hot which is going too shorten the lifespan of the engine.

(quoted from post at 22:15:06 05/20/18) Friend just bought a new Snapper 0turn mower with 25 hp B & S engine i was surprised to learn they recommend straight grade 30 wt oil in it.
Didn't Know they recommend a straight wt oil in anything any more.

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Just ask for straight oil for a two stroke Detroit diesel . The specs will be SF-2 , a low ash spec oil .

Well sir, my initial reason for running funn syn was just that....I followed the hype. Things in the air cooled engine department must have changed. My V twins blow a lot of air out from under the shrouds and the oldest is the Honda on a 2005 44" Z Fastrak. To have the fins on the cylinders cooler than the engine oil was a surprise to me. I still use the syn but don't feel the need I once thought air cooled engines warranted. Maybe older engines do run hotter. I don't recall air blasting out like it does now.

When I was growing up I recall mom and dad running Texaco Havoline HD 20 in the winter and 30 in the summer down in S. Tx. Had a Texaco station at the end of the street and they would come and get moms car, do what was needed and bring it back. Neat.

I did some more mowing at a different location this evening with a zero turn mower with a Kohler Command CV25 engine and 61" deck. Outdoor temp was about 80 deg F. After an hour of mowing I checked the oil filter external temp with an Infrared gun and found that it was 218. That is an ok temperature and will boil off any water that might have condensed in the crankcase. However, the oil temperatures that I measured today are concerning because it was a cool day here. When the outside temperature gets over 90 deg F I believe these oil temperatures would be approaching 250 deg F, which is generally considered in the thermal breakdown range for conventional 30w oil. If that proves true I am going to change to Amsoil 10w30/30w which should have a slightly higher safe operating temperature compared to conventional oil. I hesitate to do this because Briggs and Stratton says that oil change intervals can not be extended when using synthetic oil. I think that they are right on that issue. Small engines can load the oil with soot and particulates more quickly than liquid cooled engines, and once the oil has the maximum amount of particles in suspension that it can carry it is time for an oil change.

Harley-Davidsons have always had roller tappets which do not require zinc in the oil.