Synthetic oil bad in a lawnmower? Any truth in this self proclaimed experts statements?

OVERKILL

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Thanks a lot for such a thorough post. This is what I was really hoping for. It took a lot of years of casual browsing on here to pick up on this stuff. I'm still no expert but I believe I have the basics.

You are quite welcome.

If I may offer a word of advise:

Don't bother engaging with this guy. Take my comments above as confirmation of your position, which I expect you have, and just ignore him. He is just going to double-down and no progress will be made. He has taken this exchange so far into the weeds and on so many tangents that it is abundantly clear he's just trying to beat you down with rhetoric and perceived "experience" and no amount of counter pointing or factual data is going to make inroads with him. He knows it all, and for those types, enduring the frustration and exerting the effort in rebuttals is simply not worth it because you will perpetually remain at this impasse.
 
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I had a disagreement with someone on another forum that specializes in lawn equipment/small engines about whether or not full synthetic oil is dangerous to use in a lawnmower engine. They made all kinds of statements that didn't seem right to me. I'm wondering if some of the actual professional lubrication experts on this board like Molakule or others could read some of what he's said and tell me if there is any truth in it. The only source he could give me had nothing to do with synthetic vs conventional and was the basics of fluid dynamics, which obviously I don't have experience with or time to learn at this point. All of what I learned about oil has come from this forum over the past 15-20 years of casual reading. Here are 2 posts from this guy on the thread discussing use of synthetic in a lawnmower engine:

"What people fail to appreciate is engines are designed for a specific type of oil .
That includes the size of oil holes so that the right amount of oil will flow through them to do the job required and there will be sufficinet oil pressure left in the system to lubricate parts further down stream of the oil pump.
They also fail to understand that the flow charasterisc of oil under pressure is totally different to oil flow under gravity which is how the numbers on the front of the bottle are measured.
So all that the numbers on the bottle actually tell you is how the oil will drain back down the drain holes to the sump .
So for instance a synthetic oil that flows faster & easier will not provide enough oil to the last 2 journals on a strait 8 engine because all of the pressure will bleed off lubricating the first 6 cylinders .
Assuming cylinder 1 is closest to the oil pump, the slippers on it will have little rivers all through them because it got too much oil by volume because to use the synthetic oil the oil holes in the crankshaft need to be smaller because the oil flows freer .
It takes years for very experienced engineers to design & test the lubrication system in anything to ensure it all works properly with the lubricant it was designed t & tested with.
Then Joe Idiot comes along and thinks just because some race driver, big brested bimbo, whoever pops up on TV and says this stuff is better it will automatically make whatever they put it in run forever .'
Some times it might make no difference and some times it will
If it makes no difference then the user is pouring money down a hole & wasting the planets resources
If it does make a difference then that door swings both ways
Some times it will be better but most times it will be worse.
However Joe Idiot never take responsibility for his own stupidity and will blame anything else other than him using an unsuitable lubricant .
Barnets got blasted from pillar to post because their clutch plates were slipping all over the place then after several years it was found that it was the owners shoving fully synthetic oil into their motorcycles that was causing the clutches to slip .
A similar story with NSK who copped a ton of warranty claims for excessive wear in roller big end bearings and crankshaft bearings
Same story, the freer flowing synthetics floated the rollers so they slid on the outer race rather than rolling .
This was a particularly big problem for Ducatti Desmo engines and to a lesser extent Harleys , made more confusing to Joe I Know More Than The Design Engineers , as latter models used synthetic oils so it must be OK to use it in older modles , well it was not ."





"IF you don't understand the basics then all you can do is put blind faith that what some one else has said is factually correct .
As you are totally unwilling to put in the work to educate yourself then you will never actually understand how lubrication works.
I started my learning curve back in 1972 in the final years of my degree with a 2 hour lecture once a week for 13 weeks.
So that is 26 hours of face to face lectures + 13 more of tutorials + 13 more of practicals + 51 of pre lecture back ground reading before lectures.
How many hours have you spent on face book ?
As for mower engine as was previously stated is all using a synthetic or semi synthetic will do is cost you more money .
But if it makes you feel good then do it all it will do is waste your money .
While their history goes back decades fully synthetic oils were developed commercially for F1 racing where spending $ 1000 / gallon on oil is petty cash.
The engines in F 1 are pushed to their max they run at a lot higher temperatures than you mower ever will and every part has been cut down to the absolute minimum weight that will hopefully stay together for the length of a race and the manufacturing tollerances are substantially tighter than your mower ever will plus the oil plays a massive part in cooling the engine , or rather keeping the internals at a constant temperature , again totally irrelevent to an ir cooled mower engine and requires a bit of maths .
Viscious friction robs power from the tailshaft so anything that can reduce it is a big + in racing.
When we raced speedway all of the engines run total loss oiling and you do notice the difference in responce between that and the same engine mounted into a Hagon frame with an oil tank for short circuit
Synthetic oils they stayed as an exotic item even during the oil crisis of the 70's when I was in college . untill California tightened emission laws then all the major engine makers found that the thinner oils allowed the engine to crank faster so the first cylinder to do a full induction cycle fired reducing the unburned fuel passed out the tail pipe thus meet the starting emissions tests for almost no developement costs.
The engines were run to destruction & oil galleries modified where necessary.
The oil companies were then told we want engine oils with these properties of the fully synthetic oils for our production engines but we will only pay $X / gallon for them .
Thus the semi-synthetic ( and that name is total BS as the oil is not synthetic & never was ) oil was born by stripping the dreaded "Dino oil" into some componant parts then recombining them in proportions that would not normally happen and that is part & parcel of the normal processing of normal oils .
All that the oil companies did was add a couple of extra distillation processes to the regular processing .
True synthetic oil, created by reacting gasses together under pressure is a different animal but you won't find it at your local discount car parts shop.

The oil companies then had a premium product that cost marginally more than the standard product but because of the hype around it could be sold for 3 times the price of regular oil and pushed it hard by extolling its better properties, most of which was almost true but none of it of any real benefit for any engine not specifically designed to run it .
So you can run it for 3 times as long as you can run standard oil before it oxadises and starts to brake down chemically.
But that is not why you change your oil
You change it to remove the acid byproducts of combustion which happen regardless of the oil used and more importantly to remove the ultra fine particulates that errode your engine the exact same was as the Colorado river has erroded the Grand Canyon , but they fail to tell you that.

As for mower engine what can I say?
Probably once or twice a year an old worn out 2.5Hp side valve B & S powered mower comes into the shop with about 1/3 of the original oil still in the crankcase burned to the consistency of triple cream on a mower that the owner has had since the 80's and never so much as checked to oil let alone change it or even top it up.

And I would imagine every tech on here would have the same thing happen to them every year
Your 1981 B & S engine will run happily of full splash lubrication and there is a good chance it was actually full splash .
So your use of it just goes to show your absolute failure of understanding of the fundamentials of lubrication inside an engine.
The tug-o-war between adheason, coheasion & gravity let alone the significance of valence inbalance at the terminals of the molecules, and the difference the shape of them makes to the flow of the oil through the galleries.

And FWIW the only calculations in OLDS are just barely high school level and mainly about temperature flow & heat removal .
Get yourself a copy & read it then if you have understood what was written you will have just enough information to work out weather you are being fed fact, fiction or hype.
As an old text book it is probably everywhere used for $ 5 rather than the $ 50 I had to pay when it was a brand new publication.

Over the years I have found oil to be like religion and those who most strongly argue about it do so from a position of blind faith.

On one of the motorcycle forums we ran a survey to see just how much the members understood about oil
The question was
Do multigrade oils get thicker as they get hotter. yes / no
Over 90% got it wrong .

In my TAFE classe I used to ask the question
What is the purpose of the detergent molecules in oil ?
In the 11 years I taught not s single student got the question correct
We put the same question in the final exam and agin just about every student got it wrong
They all correctly described the mechanism of how they work but the students could not get the "detergents clean" BS out of their heads that the advertising companies had implanted .
And if you are wondering.
The function of the detergent is to carry away the particulates that they encounter & prevent them from combining
Secondary purpose is to make the contaminants close to the SG of the base oil so they will circulate freely within the oil to facilitate mechanical removal .
You will find that in OLDS as well no maths required."
Ive run synthetic oil for years in Honda and Craftsman mowers and never had an issue.
 

ZeeOSix

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You are quite welcome.

If I may offer a word of advise:

Don't bother engaging with this guy. Take my comments above as confirmation of your position, which I expect you have, and just ignore him. He is just going to double-down and no progress will be made. He has taken this exchange so far into the weeds and on so many tangents that it is abundantly clear he's just trying to beat you down with rhetoric and perceived "experience" and no amount of counter pointing or factual data is going to make inroads with him. He knows it all, and for those types, enduring the frustration and exerting the effort in rebuttals is simply not worth it because you will perpetually remain at this impasse.
The guy the OP quoted is living in a lubrication fantasy land. Where do people come up with that kind of stuff ? ... and he said he was properly trained. 😂
 
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Oil pressure in a lawn mower?? Proved their ignorance right there! I don't think most (non-arctic operated) OPE NEEDS full synthetic, but I can't see it hurting anything.
Pressurized oiling systems are more and more common on mowers now. Not your basic 4HP push mower, those are splash oiled, but if it has a filter, it has oil pressure.
That said, I had a single lung B&S 14HP intek that ran like a top for the 20 years I owned it(no hour meter) no filter and splash oiled, have a Kawasaki 17HP FH500V with 1530Hrs on it and have a Briggs 28HP commercial turf motor, all have had synthetic or the old rotella all their lives.
 
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I have used Valvoline 10w30 semi synthetic in my lawn tractor, lawn mower, brush cutter and generator for many years. The engines have never leaked or required a top up between services.

All the machines are used between 10 to 35 degrees centigrade. In Australia I would not hesitate to use any off the well known oil brands.
 
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I generally use 10 w 30 or similar full synthetic in snowblowers and lawnmowers from the last 30 years.. no issues..
HOWEVER..
My 1986 kohler magnum m20 horizontally opposed large frame tractor engine cant use multi weight oils in my experience.
I tried 10w30 and the oil light came on at low rpms and the engine seemed to be way too hot compared to normal.
I called simplicity and they cautioned only straight 30 weight oil is to be used in that large kohler engine.
Dont know about synthetic / vs blend / vs conventional. But I know only straight 30 is going in my engines from kohler. I have a couple and have owned each 35 years. They run great and dont consume oil.

So most modern engines I agree can easily run synthetic 5w30 or 10w30 oil.. in fact I run M1 10 W 30 in my honda and simplicity snow machines. Tecumseh engines in the ariens and simplicity ... and honda engine in my generator and honda snow blower.
That has been my experience..
 

OVERKILL

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I generally use 10 w 30 or similar full synthetic in snowblowers and lawnmowers from the last 30 years.. no issues..
HOWEVER..
My 1986 kohler magnum m20 horizontally opposed large frame tractor engine cant use multi weight oils in my experience.
I tried 10w30 and the oil light came on at low rpms and the engine seemed to be way too hot compared to normal.
I called simplicity and they cautioned only straight 30 weight oil is to be used in that large kohler engine.
Dont know about synthetic / vs blend / vs conventional. But I know only straight 30 is going in my engines from kohler. I have a couple and have owned each 35 years. They run great and dont consume oil.

So most modern engines I agree can easily run synthetic 5w30 or 10w30 oil.. in fact I run M1 10 W 30 in my honda and simplicity snow machines. Tecumseh engines in the ariens and simplicity ... and honda engine in my generator and honda snow blower.
That has been my experience..

Redline and AMSOIL HD 10w-30's are basically SAE 30's. The PAO base just has the ability to also meet the 10W winter rating. You probably ran an SN PCMO "Energy Conserving" 10w-30, which would have more VII's and lower HTHS. Not sure how that would make the engine run hotter, but it could definitely result in lower oil pressure.

If you want to run a multigrade, an HDEO 10w-30 would likely work just fine.
 
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Redline and AMSOIL HD 10w-30's are basically SAE 30's. The PAO base just has the ability to also meet the 10W winter rating. You probably ran an SN PCMO "Energy Conserving" 10w-30, which would have more VII's and lower HTHS. Not sure how that would make the engine run hotter, but it could definitely result in lower oil pressure.

If you want to run a multigrade, an HDEO 10w-30 would likely work just fine.
I appreciate the info.. but I am just sticking with straight 30 weight oil in my two sunstar tractors.. 35 years old they run perfectly and I keep the oil and filters changed once a year. For lawn gear thats way more service than most people give their equipment..
Think its castrol hd 30 that I am running.. and I dont know if its great or not.. but it seems to be keeping my equipment ok.

I believe you are 100 percent correct that the multi weight oil I tried was the energy conserving labeled oil. I had no idea until I got flickering oil pressure lights on two tractors that I did something dumb.. that was at least 20 years ago and the tractors are still running great with straight 30..
 
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I stopped reading at the point he mentioned Harley Davidson. Guess he didn't know they approve and sell their own synthetic oil. I use Mobil 1 in all my OPE with no issues and this has been atleast 20 yrs.
 

350Rocket

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I used Mobil Super Synthetic 5w30 in my mower and it still looked almost new after two seasons.
I changed the oil in my 99 Briggs quantum several times the first year, because it had a leaking needle and seat and was getting fuel in the oil. Got that fixed.
It smokes on start-up but doesn't burn any noticeable amount of oil. I was changing it before storage every winter but this year I'm leaving for a second season as it still looks like new.
M1 0w40.
 
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I started using synthetic in my lawnboy about 7 years ago. First observation is that the oil level never went below the top, so the nominal normal consumption stopped. I think it's because the synthetic is much better with withstanding the heat and doesn't burn off.
 
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Pressurized oiling systems are more and more common on mowers now. Not your basic 4HP push mower, those are splash oiled, but if it has a filter, it has oil pressure.

Not necessarily. Many OPE engines that have an oil filter DO NOT have pressure lubrication.
 

CleanSump

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Not necessarily. Many OPE engines that have an oil filter DO NOT have pressure lubrication.
Can you expound on that a little bit? So the oil is filtered, but isn't supplied to the crank or valvetrain by the pump. The pump just circulates oil through the filter? Not sidetracking, just not up to date on such designs. Thanks.
 
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I have customers that still insist on using Non-Detergent SAE 30 in their power equipment engines.
Wandering off the OP's subject, but about a dozen years ago, my mom bought a lawn mower from a farm chain store. The salesman swore to her up and down that you MUST use non-detergent in her new lawn mower. If she didn't, HER WARRANTY WOULD BE VOID was what he brainwashed into her head. She purchased some non-detergent oil for her next oil change.
She then thought I was missing a few marbles when she told me that I would being non-detergent oil when I changed oil in her mower for the first time. I quietly opened up the operator's manual and pointed out what the factory said her lawn mower needed. She got quiet after that and took the oil back the next time she went into that store. I just wonder how many other customers used non-detergent oil for the life of their mower?
 
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