The Reason I think Synthetic Oil is Best for 4-Cycle Mower Engines. "Who Agrees?"

[bertsmobile1]

Re: The Reason I think Synthetic Oil is Best for 4-Cycle Mower Engines. "Who Agrees?"

If you had the slightest understanding about oils Lubrication & engine design it would be abundantly clear that if an engine will run on conventional oil it has not been designed to utilise the full potential of synthetic oils.

The closest analogy is filling your old WWII side valve engine with 100 Octane racing fuel when it will happily run on 75 wartime pool petrol.
It will chug along on hi-test gas but it won't make 1 rpm more than it did on 75 and cost more to run.
It will require less downtime scraping carbon off the piston crown but it won't run any better.

Did Briggs say to run the synthetic for 2 or 3 times longer than conventional oils ?
IF not then what advantage are you gaining ?
The cooling of the engine is a function of the heat transfer surfaces and the R value at the interface between the hot metal & the cooling medium.
Oil is a poor conductor of heat so at best will transfer some heat from the hot head & cylinder down to the sump where the action of the flywheel & counter weight will actually increase the heat and because the sump is out of the cooling air flow and most times shielded by the bottom of the mower floor the rate of heat loss is very low.
Now unlike your NASCAR, the primary method of lubrication inside your mower engine is splash.
So while the NASCAR engine throws fairly clean oil out off the big end up into the cylinder, and all bearing run in cleaner filtered oil, your engine splashes the dirty oil sitting in the sump up the cylinder walls.
The bottom bush runs in the same dirty oil , along with any grit, carbon particles , acid combustion by-products and dust sucked inside.
On a lot of engines the upper bush also is splash lubricated and it is only the oil that is actually pressure fed into the big end that is filtered and that only happens on engines that actually have oil filters, which is not as many as you would think.
AFAIK the only mower engine with full pressure fed lubrication currently in production are the Kawakasi ones which is one reason why they are $ 500 + more expensive than the Kohlers.
Even then , there is no seal between the crankshaft and the sump so the lower bush still runs in the dirty sump oil

Now for some of the contractors who have no choice but to mow 25 deg or 100 deg and do 300 + hours a year, then there is an advantage which makes it worthwhile.
As for Joe Blow home owner it will not make the slightest bit of difference apart from making them think their manly protuberance is bigger than the bloke next door.

For many many many years I have been advising motorcycle owners that the best oil for their vintage engine is the stuff they just drained out at a shorter interval than recommended.
I run 100 year old engines on Gulf Western ( local blender ) 25w75 at $ 3.95/ litre ( ~ 1 quart) and I never have any oil related engine problems.
Because it is cheap I change it every time I use the motorcycle, just before I put it away.
Born again motorcyclists buy really expensive ( sometimes synthetic ) oil then expect it to last 20 years because they only ride it 200 miles a year.
I pass their pretty polished catalogue correct bikes on the break down trailers regularly.
Then there are the fools who try to run full synthetic only to find it will not make an effective seal between the rings & the psiston and because it is subdstantially slipperier than std oils actually prevents the piston rings bedded into the cylinder walls.
The post WW II motorcycles get SAE 30 mower oil which I buy for $ 2.45 / litre and same story, get home, drain the oil refill and the bike is ready for the next outing and I do about 30,000 miles on these bikes per year.

99.999999999999999999999999999999999999999999999999999999999999999999999999999999999999999% of the oil related problem that come into the workshop is because the owner has not checked the oil and there wasn't any.
Even then very few of them had fully cooked oil, some was a bit thick due to high concentrations of particulate matter, but not cooked.

Now if you really want to know, search the forum for "engine temperatures".
While not particularly good, nor done properly a list member did at least make a reasonable effort to plot engine temperatures over a variety of operating conditions & ambient temperatures.
These were all surface temperatures which will have to be extrapolated to get interiour temperatures but not too bad and from memory he did some oil sump temperatures as well.
Do this enough & you can make tables which are useful.

At temperatures above 250 deg F the alloy used in the cylinder head starts to soften which allows bolts to loosen and valve guides to slip so having an oil in there that is stable above this temperature is totally useless.

But as stated before.
If it makes you feel good, do it. It is your mower & your money

 

[mrstan]

Re: The Reason I think Synthetic Oil is Best for 4-Cycle Mower Engines. "Who Agrees?"

Hi guys,

I looked into this topic when I was replacing my car's oil as well. What I found was that the synthetic molecules are smaller than the conventional molecules. for this reason, the oil manufacturers were answering questions related to blow-by and oil consumption regarding full synthetics. What I took away from the discussions was that the synthetic oil can get into places where conventional oil
simply can not fit. This comes into plat when you have an engine with very tight tolerances in the journals and passages. The major line of the discussion revolved around the assertion of leaks caused by the synthetics which did not happen with conventional. Newer auto engines hold tighter tolerances obviously as you can see their oil change cycles are extended to 7000 miles is many instances... Compression is heightened by the same tolerances in the rings as well.

with this as background, my outtake was that lubrication is heightened because of the smaller mechanics of the molecules for sure, but care must be taken to avert the leaks since it can seep out of smaller fissures. I am not sure of the journal tolerances on a lawnmower engine are exactly, but I would assume they might be somewhat wide (will have to look mine up as well).

As to the temperature of lawnmower engines, I think it should be around 250F typically. Remember Gasoline flashes at 536F, so we do not want the engines to get around 400 like I saw in some post earlier was suggesting.
Car engines typically run around 220 to 240F, but they are normally water-cooled where the lawnmowers generally rely on airflow to draw heat away. The heat characteristics of the oil should be around the same as a typical automotive engine in other words.

I do not know how to really determine if synthetic is better than conventional in the small engine world because lubrication is done with a smaller amount with smaller components (This is why we have to change the oil so much more often too). I read where synthetic oil dissipates heat more readily than conventional, but also that it oxidizes faster as well. IS the quantification of significance though? I do not know any numbers or even if this has been actually tested clinically. In my opinion, its a lawn mower... LOL Just use best judgement I guess. Maybe someday someone with lots of time on their hands will actually study this stuff all out.

 

[bertsmobile1]

Re: The Reason I think Synthetic Oil is Best for 4-Cycle Mower Engines. "Who Agrees?"

Just so we all know what we are talking about here.
Synthetic oils are not synthetic.
They are not some magic conerting water into oil.
All synthetics are is an extension of what we already do with hundreds of products.
In place of refining oil to make a particular grade or product, we take it apart then add the bits we want back together.
It originated in Europe so they could use their high ash crude.
We do the same thing with wheat, corn, barley and milk,
Depending upon how far it was taken apart determines weather it gets called Fully or Semi Synthetic.

To utilise full synthetic oils the piston ring side clearence has to be reduced to almost nothing, otherwise it can not form a seal between the ring & the ring grove and the engine will leak compression.
There are a lot of other examples but that is the one which will make most sense to those without a fuller understanding of engine design & lubrication.
Low ash synthetics are great for 2 strokes as they disperse better in the fuel and condense back into oil better in the crank case, they are more slippery ( because we control the size & shape of the molocules ) so can be used in far mre dilute concentrations so we have low smoke low ash 2 strokes, brilliant, except the EPA's in almost every country are bending over backward to ban 2 strokes.

 

[RoofTopPigeon]

Re: The Reason I think Synthetic Oil is Best for 4-Cycle Mower Engines. "Who Agrees?"

Low ash synthetics are great for 2 strokes as they disperse better in the fuel and condense back into oil better in the crank case, they are more slippery ( because we control the size & shape of the molocules ) so can be used in far mre dilute concentrations so we have low smoke low ash 2 strokes, brilliant, except the EPA's in almost every country are bending over backward to ban 2 strokes.

bertsmobile1; what do you feel is best for 4-cycle engines then?
For 4-Cycle's would you just go with the manufacture recommendation?

 

[bertsmobile1]

Re: The Reason I think Synthetic Oil is Best for 4-Cycle Mower Engines. "Who Agrees?"

It depends upon the engine.
Side bangers all get strait SAE 30 mower oil
Honda walk behinds get 10W 30 mower oil for residential customers & 10W 40 for commercial customers.
late model kawakasi get 10W 40
All carby Kohlers apart from those under warranty get SAE 30
EFI Kohlers get 10W 40
Inteks get SAE 10w 30.

All of these a standard LAWN Mower oils

You see there is no such thing as the best oil for all.
I keep 5 gal of fully synthetic 5W 40 mower oil because 1 customer wants me to use it but he still gets his oil changes done at the same hours a if it was std oil and he pays $ 55 / litre.
He likes it because he is impatient and the mower fires up before the ignition key gets to the end of the rotation.

I go through 4 x 44's of 30 for every 44 of 10W 40 and 2 of those for each 10w 30.
Climate here is similar to Southern California and we mow all year round.

Synthetics are really a con but to comply with emissions at start up laws car companies specify them rather than modifing their engines.
That way you pay & they don't

OTOH the synthetic gear oils are a different kettle of fish, worth every extra cent but then Joe Average would only change the gearbox &/or diff oil once or twice over the full life of the vehicle.
If I was trying to squeeze 150% out of a race engine then it is a different matter but you need to understand lawn mowers are really old technology and so understressed it is not funny.

Think about it.
My 1940 505 cc BSA side valve single is rated at 13 Hp
My 1972 499cc OHV single BSA is rated at 48Hp.
A brand new 498 cc OHV briggs is rated at 15 to 19 Hp

Nascars would be running 3 to 5 times the Hp/cc as a mower engine.
They are working hard and need every little bit they can get.

 

[Ric]

Re: The Reason I think Synthetic Oil is Best for 4-Cycle Mower Engines. "Who Agrees?"

Bert, your fighting a battle you can't win.:laughing: You'll never convince these guys that there's no advantage to running synthetic oils in a lawn mower. Fighting this battle is not unlike the fishing tackle industry and all the lures and they put on the market with all there claims. There lures are basically designed to catch fishermen, not fish and those guys, me included :laughing: just keep spending the money for all the gimmicks and looking for that miracle lure.

Synthetic oils in a lawn mower is nothing more than the industry gimmick. I've run mobile 5000 10w30 in all my Kohler and Kawasaki engines forever and never had any issues and here in Florida outside temps run between 85 and 105 degrees all summer and I'll run 4 to 5 hours sometime more every day. Change your oil every 50 hours with a filter change and you wont have any issues but as you said earlier if you want to run synthetic, spend the extra money and it makes you feel good run it.

 

[possum]

Re: The Reason I think Synthetic Oil is Best for 4-Cycle Mower Engines. "Who Agrees?"

Synthetic oils are not all that expensive anymore. NAPA has their synthetic on sale 2 to 4 times a year for 3 bucks a quart. Six years worth for 12 bucks on a pushmower. Nowhere in this small town I liver in can I get any oil for less. Most places it is 4 or 5 bucks a quart for conventional oil. I know people who have not left town for 5 years. Most of the time I can buy synthetic with a rebate for at or very near the same brand conventional. Sometimes for less. Mobil being one of them. But I do have to leave town. The synthetic gear oils are supposed to be a great deal better as was suggested but I can tell no visible difference after inspection of small gear boxes with 5000 hours on them. Synthetic oil runs more quiet in small engines but I doubt much more than that.

 

[sidemouse]

Re: The Reason I think Synthetic Oil is Best for 4-Cycle Mower Engines. "Who Agrees?"

It depends upon the engine.
Side bangers all get strait SAE 30 mower oil
Honda walk behinds get 10W 30 mower oil for residential customers & 10W 40 for commercial customers.
late model kawakasi get 10W 40
All carby Kohlers apart from those under warranty get SAE 30
EFI Kohlers get 10W 40
Inteks get SAE 10w 30.

All of these a standard LAWN Mower oils

And what goes in a Generac or do I just use the Kohler oil, wait how's that work again?
All that does is confuse the consumer.

Keep it simple...
One oil, all 4-cycle gasoline engines.
I have close to 30 engines on my property, all different makes and models.
Someone expects me to carry fourteen different kinds of oil, preferably several quarts of each?

Ok that's good, here's my Toro 30197 cv-15t, what's it take, 10w-30?
Oh you wrote it down, did you, where's that piece of paper again...
Your quote: All carby Kohlers apart from those under warranty get SAE 30
That's odd because the CV-15t Kohler Owner's manual recommends 10w-30 as per the manufacturer.
Who are we kidding?

That's why I run 5w-20 full synthetic in all 4-cycle gasoline engines.

Guess what oil goes in my Honda engines?
Yes, I have at least four or five of these...
If you guessed 5w-20 full synthetic you would be right!
Better yet there is no other 4-cycle engine oil on my whole property, so if you grabbed a quart you got it.
How simple was that?

No looking up charts, no hunting down owner's manuals, no pecking through the inventory to find that one special quart bottle.
Also eliminates the off chance of running air compressor oil in my gasoline engine, or chainsaw lube.
Yeah I forgot, I have to carry chainsaw lube, air compressor oil, oh and 2-cycle mix as well.
One oil, all 4-cycle gasoline engines.

And if 5w-20 full synth doesn't float your boat pick one that does, then stick to it and if things don't work out at least you'll know where to start.
One oil, all 4-cycle gasoline engines.
Simplifies life a whole lot.

 

[RoofTopPigeon]

Re: The Reason I think Synthetic Oil is Best for 4-Cycle Mower Engines. "Who Agrees?"

That's why I run 5w-20 full synthetic in all 4-cycle gasoline engines.

Thanks; sidemouse;
I will run my Personal Preferance of Full-Synthetic
Valvoline 5W-30 with Max Life Technology. In my 4-Cycle Engines.

 

[DK35vince]

Re: The Reason I think Synthetic Oil is Best for 4-Cycle Mower Engines. "Who Agrees?"

I use one oil, Rotella T-6 5w-40 synthetic in my tractor, garden tractor, zero turn, ATV, generators, push mowers, water pumps, pressure washer, Etc.