Bad M1 0W-40 Experience in Snowthrower

[pmt]

My current snowthrower has a Briggs & Stratton 8 HP 4-cycle engine (flathead, not OHV). The engine does not have a lot of hours on it, and I have have always used Mobil 1 5W-30 oil in the crankcase with good starting and low oil consumption. This Fall when I changed the oil, I put in M1 0W-40 - thinking it might be an ideal oil for the application - good cold flow and higher viscosity for the air cooled engine heat.
But after putting about 3 or 4 hours operation on it, I checked the oil level and found it was way down! I haven't yet refilled, so don't know how many ounces it has consumed. But it is consuming much more M1 0W-40 than it ever did M1 5W-30. I will refill it with 0W-40 and keep a closer eye on it.
Anyone have any theories on why this old style flathead air cooled engine drinks 0W-40? I've seen several people comment that their car engines consumed less M1 0W-40 than when they used M1 10W-30 or 5W-30.
Thank you.

 

[JohnBrowning]

If I had to take a guess I would say that it is due to shearing and boil off! M1 0W40 is not the most shear stable oil! AIr cooled engines need a very shear stable oil. If you really need a good oil for that snow blower try Amsoil 5W30 or Redline 5W40! You could also go back to M1 5W30 or 10W30. Some of that oil that burnt off is in the engine to stay in the form of deposits. THe last thing you need especialy in an air cooled flat head is deposits!!

 

[Bror Jace]

pmt, is cold start ability a real must for you? If this thing is garaged, I think you'll have a hard time beating the 15W40 fleet oils like Pennzoil Long Life or Chevron Delo400. I use Schaeffer synthetic blend in 15W40. Pumps at about the same temp as a conventional 10W30.

We've seen M1 0W40 shear down and air-cooled engines are notoriously hard on oil. This may be what's happening to your oil.

If cold starting is a serious concern, consider one of the oils JohnBrowning recommended or Mobil Delvac 1 in 5W40. The stuff may be a bit difficult to find but nearly everyone who's used it raves about it.

Lastly, you'd be better off changing your oil at the end of the season as opposed to the beginning. Best to let the internals sit in a bath of fresh oil for months rather than used, contaminated oil.

--- Bror Jace

 

[userfriendly]

My 6 HP lawnmower does the same thing with Pet-can 5W40, but I'll continue to use the stuff because the oil does not sparkle with glitter and stays clear longer than the other oils I've tried.
The last time I mowed the lawn, I found another vehicle.

 

[harper]

A bit off topic but does it really matter on quality of synthetic oil whether Group III or not since the motor's are pretty primitive at best. I need to do the the first oil change at 5 hrs, (nearing that) and they recommend synthetic. The reason I ask is SuperTech Synthetic in garage typically for lawnmower is available for the first oil change of new Simplicity snow blower (9HP Briggs & Stratton Intek).

 

[pmt]

Thanks all for the input. I have some Delvac 1 left over from an oil change, so I think I'll try that. I'm a little confused on what causes an oil to shear down quickly. I can see how highly loaded gear drives or high pressure pumps could shear oil. But I thought high oil temperatures (like in an air cooled engine) mainly oxidized oil, thus thickening it. Can high heat also contribute to rapid shear down?
My snowthrower 8 HP B&S engine does not have an oil pump, just a slinger on the connecting rod (oil splash system). The camshaft is gear driven, but I don't know how heavily the gear teeth are loaded.

 

[Bror Jace]

pmt, high heat also breaks up the long-chain polymer molecules which make up the oil's viscosity index improvers.

Heat activates this goo and makes it thick ... but high heat, along with mechanical stress, break it down and thin it out.

--- Bror Jace

 

[Mike_dup1]

fyi

I have used nothing but synthetic oils in my Ariens snowblowers since the 1970's. Always used 10W-40 but my newer 1999 13hp 36incher has been run with 0W-30. It rarely needs any oil added.

I also changer the oil every fall but only because I am so sick or winter that I forget about the snowblower and have been know to not change the oil for several years. Maybe its luck or maybe it the oil but I have never had any engine problems with any of them. I have been selling the used ones and buying new about every 8 yrs.

I have used Amsoil since 1977 but before that it was Mobil 1.

 

[TooSlick]

The rate at which a multigrade oil shears is a function of both heat and repetitive loading. This is why it's difficult to simulate in a bench test.

What you are doing to the polymer molecules is similar to thermal cracking, as well as mechanical shearing. One of the main reasons why turbocharged engines shear oil so badly is the localized heating effect as the oil flows through the turbocharger bearings. As it flows rapidly through these small orifices it is heated and sheared at the same time.

Any engine that runs very hot, like the 3.0L, Toyota V-6, or a commercial diesel, will shear the oil. My 2.4L Tacoma engine uses the same gear drive on the exhaust cam as the Camry, but hardly shears the same oil that shears in the 3.0L, V-6. The reason is that my average oil temps are much lower... This is a result of the 5.5 qt oil capacity of the 2.4L engine and excellent airflow through the engine compartment and across the exposed oil pan.

The oil pan in a truck is also significantly higher off the ground then in a passenger car, so there is less radiative heating from the asphalt. Measure the temp. gradiant from a hot road surface to two feet above it in the summer and you'll see what I mean. The "delta T" can be up to 50F ....

[ December 19, 2003, 03:27 PM: Message edited by: TooSlick ]

 

[Hankrr]

I've been using Mobil-1 0w-30 in my John Deere snow blower for about four years. Mine has a 7 hp engine.

I haven't noticed mine using any oil at all. none. I like the 0w-30 for easy starting since it don't have electric start and I have to pull start it up........