B&S Oil Recommendations

taylorkh(NC)April 9, 2010

It appears that Briggs makes the same recommendation for oil regardless of engine type from the ancient side valve models to the more modern OHV engines. Two points of curiosity to me are:

1) The use of straight 30 Weight oil

2) The acknowledgement of only 10W30 muti-viscosity oil

Multi-vis oils have been in use for more than half a century and were developed to overcome the tendency of straight weight oils to become too thin at high temperatures to provide adequate lubrication. B&S indicates that air cooled engines run hotter. So why is HD30 still recommended?

Briggs also states that oil consumption may be increased when using 10W30 at higher temperatures. Is not that why we have 15W40 or 20W50 weight oils? And, since a 10W30 oil is supposed to have the same viscosity at high temperature as a 30 weight oil the claim of increased consumption sound a little suspect.

My JD 314 has a Kohler side valve engine. It likes HD30 and does not tolerate anything else. I tried some Valvoline 20W50 racing oil which I had left over from my RX7. The engine drank a quart of oil over a 25 hour change interval. It never used oil with HD30. Then again the design of the engine dated back to the days of the dinosaurs from which the oil was made :-)

So now I am puzzling over the best oil to use in my new Scag Freedom Z with a Briggs Intek OHV engine. The dealer claimed that Briggs sent them a service bulletin recommending only HD30 in temperatures over 90F (although they could not find a copy of it when I asked).

In my prior mower, a JD SST18 with a Briggs made OHV V twin engine, I used 10W30 per JD recommendations. It never used oil between changes over 9 years of use.

My instinct tells me that something like Rotalla T 15W40 would be ideal for this application. The mower will be run mostly in the summer but on occasion during cooler weather.

Comments or snipes?


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You can run any of the oils mentioned, Straight 30w only in summer if you run you LT in the winter months then it would need thinner Weight. It's not problem after the engine heats up, but start up on cold or cool days. Once the 30w get hot is runs like water anyway.

Syn oils could be left in little longer, but when it gets black and gooey and don't drip off the dipstick it needs changed. IMO you should change the oil at least twice a year and the filter once a year. THE idea is to have clean oil in your engine during the hot summer months when it works the hardest. If you are in good non-dusty conditions then the oil will stay cleaner longer.

IMO you should change your oil in MAY at the beginning of the summer, in mid or late JULY when it really hot, and in sept/oct. with the filter. If you do that you will probably never experience a oil related problem (unless you over fill it or run it low on oil) and your mower may not use oil between oil changes just like you have already experienced with the JD.

    Bookmark   April 9, 2010 at 1:01PM
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My c/c B/S 23 hp manual states st. 30 wt. or 5-30 0r 10-30. Syn oil. Also that 10-30 might cause premature oil burning. I am thinking about using 5-30 mobil one , I used it in my kholer engine had good luck with it. The summer weather here in central Va. is hot and sticky.

    Bookmark   April 9, 2010 at 6:46PM
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I'm sure that there are exceptions, but generally speaking 40w oil can me a bit much for small engines. Rumors or fact that it caused foaming and lube breakdown. Would it with the displacement of our engine? Your call. I just use 30W (straight or 10w30 synthetic if requested.) You seem like you want to ultra care for this, and if so- use synthetic oil. Oil people will tell you that 30w regardless of the ppd is the same at operating temperature. Yet, I've been in service schools that say straight 30w handles the heat better. All the more important to do the things that keep it cooler. Clean and run it wide open.

    Bookmark   April 9, 2010 at 11:06PM
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"If you are in good non -dusty conditions then the oil will stay cleaner longer"...can someone explain this comment?????
How is the dust getting into the oil????????

    Bookmark   April 10, 2010 at 7:26AM
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Here is an interesting link on oil from the perspective of use in motorcycles (which are high performance and mostly air cooled). I think that it may be applicable to air cooled engines on lawn equipment as well.


Here is a link that might be useful: All about oil

    Bookmark   April 10, 2010 at 8:30AM
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It's going to be hard to some that really don't understand, but I will try. Now if your not one don't get all hyper!

"How is the dust getting into the oil????????

THROUGH THE air inlet passage way, when you remove the dip stick, and through the AIR FILTER it self It don't block microscopic particles.

I also clean my spark plugs before I remove them? Why would I want to do that?----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- TO KEEP THE DIRT (SAND) from dropping into the combustion chamber and causing bore scratches.

    Bookmark   April 10, 2010 at 10:13AM
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The air cleaner cover on the 8hp B&S on my Simplicity 728 says Summer SAE 30, 10W-30, 10W-40
Winter SAE 5W-30, 10W-30

I have the last printed copy of the owners manual for the 8hp B&S and its says SAE 30 for summer or Synthetic 5W-30 or 10W-30 in all temps. 1989 and newer say no non-synthetic mutigrade oil because of the emmissions junk and that causes them to run hotter because or leaner fuel/air mixtures. Where the old engines with out emissions junk run cooler because of richer fuel mixtures. Any B&S manual from 1960-1988 says you can 10W-30 or 10W-40 in summer.

    Bookmark   April 10, 2010 at 1:25PM
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I've been using 10-30 Mobile One in my 16hp briggs vanguard for 11 years now. I noticed the briggs ran much cooler using the Synthetic. A lot cooler. The color stays very clean looking between oil and filter changes. I now have a 30 hp Kohler that I'll use the 10w 30 Kholer oil and filter until the warranty runs out. But I swear on Mobile One.

I need to get out and run a mower and trimmer NOW!


    Bookmark   April 10, 2010 at 1:57PM
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rcmoser...again your wisdom and insight never ceases to amaze me.

    Bookmark   April 10, 2010 at 3:20PM
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