OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines Engine Oil for B&S I/C Series

In the engine manual for my Briggs and Stratton 850 I/C it says that it takes 10W30 synthetic oil. I have found it hard to find this spec except for Penrite synthetic fortified 10W30 (i.e. not a true synthetic) which specifically says it is not friction modified. The B&S manual doesn't say antything about friction modified.

I have found full synthetic Amsoil in a 10W30 but it doesn't say whether it is suitable for B&S engines, although it is very good oil. I can't see any reason why it isn't suitable but of course I am keen to know for sure given I have a four year warranty to keep current. I am also keen to avoid the standard monograde mower engine oils which are mineral based and in my experience prone to sludging.

Anyone have an answer or know of a full synthetic 10W30 approved by B&S?

Pete, can you post the long series of B&S identification numbers from your engine please? On the older ones they are stamped onto the cooling air cowl, but on the more recent types they could be in several places. At present I have no idea what engine model you are talking about. We need to get the right information, and that requires that we be talking about the right model.

Im not sure what the oiling system in the 850 involves, but sludging of the oil is your filter in a splash lubricated engine. But then this might be pressure.
Must be a reason why they specify the 10W30.



I would be going to a briggs dealer and asking for briggs 10W30 oil. They should have thier own brand or a supply of some.

The engine is simply a 120000 series. The only number I found on it is ABSXS.1901VJ 279875 if that helps.

By the way, I re-read the manual. It says 10W30 for a limited temperature range and it says above 27degC it may cause accelerated oil usage. The correct grade in the manual for full synthetic is 5W30. Which makes things much easier. Example, Nulon full synthetic 5W30 is API SM grade so easily passes the SJ or higher requirement. I put some of this in one of my Honda GCV160s and teh starting is noticeably easier! Will try in the B&S once my five hours is up.

The model number for the 850 is 12Q900, where the 00 depends on specifications. For plain main bearings the first 0 really is 0, and for a recoil starter the second one is 2. Hence your engine is probably a 12Q902. Somewhere on it that model number is given, followed by the type number and the date code. The engine differs from the 800 (12R900) in having an iron sleeve and double-element air filter - these are traditional I/C differences. All of the 800 series (800, 850 & 875) are 12 cubic inch (190 cc) OHV vertical crankshaft engines, and they all have an optional oil filter available. The 875 does not have the I/C features, but has 3% more torque.

So far as oil is concerned, the recommended grade is SAE 30W if the ambient temperature is above 40 degrees Fahrenheit, or 4 degrees Celsius. Briggs have always recommended SAE 30, not multigrade, for temperatures within the common range, and still do. Their reason is the desire to keep oil consumption within reason. A multigrade oil is made from a base stock (the actual oil, in other words) with the lowest viscosity they quote, and sufficient viscosity index improver to achieve the highest viscosity they quote at a very high temperature. Unfortunately oil consumption depends primarily on the actual base stock viscosity. Your SAE 5W-30 is made from SAE 5 oil, and it will pass through your piston rings like a goose on castor oil. Here is the oil change service procedure for the 800 series:
http://www5.briggsandstratton.com/eu/en/maintenance_repair/basic_engine_care/changing_oil.aspx

"For optimum performance, you should change the oil in your small engine after the first five hours of use and then, every 50 hours of use:

"Use Briggs & Stratton SAE 30W Oil above 40°F (4°C) for all of our engines.
Check oil level regularly.
Air-cooled engines burn about an ounce of oil per cylinder, per hour.
Fill to mark on dipstick. DO NOT OVERFILL
Change oil after first 5 hours of use, then after every 50 hours or at the beginning of the season."

Yes, Briggs also permit the use of their house-brand of synthetic 5W-30, which is usable even at very low ambient temperatures, but "optimum performance" requires SAE 30W, provided ambient temperature is at least 4 degrees C.

I appreciate teh comment on monograde but I would suggest you try an experiment. Fill your engine with monograde and start it. Then, change the oil out and try with the more common 10W30 per Honda, or in this case the 5W30. The difference in startability is noticeable! I just changed my Mum's Honda mower over to 5W30 synthetic and she can now start it first time everytime.

Pete, I do not dispute that light oils have lower viscosity than heavier oils. That does make it easier to pull the starter on a cold engine, and it also makes it easier for the oil to get past the piston rings. B&S authorise the use of 5W30 in their engines, so you are not contravening their instructions by using it. You will certainly use more oil, and you may incur a higher wear rate under severe operating conditions. On the positive side, you will reduce the frictional horsepower whenever the engine is not running hot, and therefore save a small amount of fuel. For what it is worth, Honda recommends the use of a multigrade oil in their mower engines, and Briggs do not. Either Honda is more confident about their piston rings, or they are more mindful of how difficult it is to get monograde.

If it significantly helps your mother to cold-start her mower, and that otherwise would have been difficult for her, I can well understand you using the light oil in her mower.