Author Topic: Question about petrol/gasoline engine oils  (Read 5311 times)

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Offline HalcyonTopic starter

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Question about petrol/gasoline engine oils
« on: August 14, 2023, 06:06:19 am »
I'm about to do a service on my petrol lawnmower next weekend which involves changing the engine oil.

The Honda manual specifies that it should be "4-stroke motor oil" with an API category of SJ (or better) and either 5W-30 or 10W-30 viscosity (I'm leaning towards using 5W since I live in an area with a relatively low ambient temperature throughout most of the year, compared to the suburbs of Sydney).

My local store has decent brand fully synthetic oil for $35 for 5 litres that exceeds the minimum SJ spec listed in the manual (this one is SN), but they also stock "speciality oils" for garden equipment and other small engines which are specifically labelled 4-stroke oils with a small 1 litre bottle costing $28 (which is also labelled "premium mineral oil").

What's the difference? Is there any reason I can't use the far cheaper oil designed for car engines, provided that the viscosity is the same as specified in the manual? Surely if it's good enough to go in a modern car, it's good enough for a lawnmower?

 

Online DavidAlfa

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Re: Question about petrol/gasoline engine oils
« Reply #1 on: August 14, 2023, 06:48:27 am »
I don't think there's any difference except the hole in your pocket, "Premium mineral oil"? Sounds like a rip-off.
I'd put the synthetic one without thinking twice, better oil, cheaper, it's no brainer!
« Last Edit: August 14, 2023, 07:00:55 am by DavidAlfa »
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Offline floobydust

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Re: Question about petrol/gasoline engine oils
« Reply #2 on: August 14, 2023, 06:58:55 am »
They might have specified "4-stroke motor oil" to avoid confusion with "2-stroke motor oil" which if mixed up ruins an engine in no time.
The expensive specialty oil I believe is "non-detergent" oil. In the old days, the concern was about foaming with splash-lubricated small engines, and since they have no oil pump, something about sediment needing to settle down and collecting in the bottom. But they used metal additives like zinc which are out of favour and expensive nowadays.
There's some videos frothing up non-detergent oil and finding it did worse compared to modern oils, so I don't see an advantage in a modern engine.
Non-detergent oil has a place in transmissions and air compressors so it still exists.

I would just use 10W30 synthetic motor oil. Air-cooled engines generally run hotter than car engines, i.e. I find a 5W20 can get water thin when hot, supposedly great for fuel economy with lower frictional losses. Small engines warm up fast but I'm not sure what temps you consider cool. Here you can start and run a snowblower when it -20°C and 5W30 is good.
Honda lawnmowers I see the majority are using 10W30 motor oil, they have a plastic camshaft too so I would not use any old school oil.
 
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Offline HalcyonTopic starter

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Re: Question about petrol/gasoline engine oils
« Reply #3 on: August 14, 2023, 08:07:42 am »
Thanks for your advice guys. I'll probably just stick with the synthetic 10W-30 as it's cheaper than buying small bottles of these so-called speciality oils. Both my mower and line trimmer take the same oil, so it's easier just to keep a larger bottle on-hand. Fuel economy doesn't matter to me, we're talking about a few dollars per year (if that). I just don't want to risk damaging the engine with the wrong oil. In terms of temperature, I'm unlikely to be mowing the lawn in anything under 10 degrees C anyway.
 
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Offline Benta

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Re: Question about petrol/gasoline engine oils
« Reply #4 on: August 14, 2023, 06:32:14 pm »
There actually is a difference, which is well known to owners of vintage cars and motorcycles (I'm one).
The modern synthetic oils have additives to absorb particles (mainly soot) in the oil and carry them through the oil filter (or for fine particles to just keep them suspended in the oil).
The older minerals oils function differently, the idea is to deposit the particles in the bottom of the sump.
Now whether this difference matters to a garden machine is doubtful. Personally, I'd just buy the cheapest 5W-30 you can get. It's not likely that a garden machine will rack up 100k miles.  :-DD
 
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Offline djsb

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Re: Question about petrol/gasoline engine oils
« Reply #5 on: August 14, 2023, 06:54:18 pm »
It's also important that the oil you use is compatible with any clutch that may be in the engine. Does the lawnmower have a wet clutch or any clutch at all? I know that this is important where motorcycles are concerned (I'm a sometimes motorcyclist) but I'm not really familiar with lawnmowers. Just something to maybe consider?
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Offline Monkeh

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Re: Question about petrol/gasoline engine oils
« Reply #6 on: August 14, 2023, 07:05:03 pm »
If you've got a decent local tool shop they probably keep the 1l bottles for more like $10-15 - heck, a quick search just found Briggs branded 30 weight for $12.65 down under, and Bunnings keep the same for $14.88. You're probably only going to need about half of that, so if you've no use for the remaining 4.5l of car oil, that might be less wasteful.

But really, for a lightly loaded occasionally used small engine, as long as there's actually oil in it it's going to be fine.
« Last Edit: August 14, 2023, 07:08:11 pm by Monkeh »
 

Online DavidAlfa

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Re: Question about petrol/gasoline engine oils
« Reply #7 on: August 14, 2023, 07:27:45 pm »
"if you've no use for the remaining 4.5l of car oil" - (Most) engines normally last for more than one oil change!  :D
The oil won't degrade or anything, as long as you keep the can closed.
« Last Edit: August 14, 2023, 07:30:41 pm by DavidAlfa »
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Offline Monkeh

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Re: Question about petrol/gasoline engine oils
« Reply #8 on: August 14, 2023, 07:28:44 pm »
"ifyou've no use for the remaining 4.5l of car oil" - Engines normally last for more than one oil change! :D
The oil won't degrade or anything, as long you keep the can closed.

While this is true, space on my shelf is worth more than oil sitting around doing nothing..
 

Offline u666sa

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Re: Question about petrol/gasoline engine oils
« Reply #9 on: August 14, 2023, 08:01:46 pm »
Whatever man. Buy the cheapest ausie 10-30 oil and call it a day.
 

Offline tautech

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Re: Question about petrol/gasoline engine oils
« Reply #10 on: August 16, 2023, 08:35:08 am »
Both my mower and line trimmer take the same oil, so it's easier just to keep a larger bottle on-hand.
How so ?
If your trimmer a 4 stroke ?
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Offline joeqsmith

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Re: Question about petrol/gasoline engine oils
« Reply #11 on: August 16, 2023, 08:13:24 pm »
For the most part I use full synthetic in all of my 4 stroke gasoline engines.   Even the small engines like my generator and such get it.  I think the generator requires changes after 50hours of operation?

I used to run methanol in one engine which required an expensive special oil along with a top end oil additive blended into the fuel.   Methanol is fun.  When I switched back to gasoline, I was using a cheap grade non-synthetic.   The oil is changed after only few miles of use anyway.  The problem was the formula changed over time due to ever changing emissions laws and I switched to a race only semi-synthetic that was better suited. 
« Last Edit: August 16, 2023, 10:37:37 pm by joeqsmith »
 

Offline Tomorokoshi

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Re: Question about petrol/gasoline engine oils
« Reply #12 on: August 16, 2023, 08:38:07 pm »
1. Use only RoHS motor oil.
2. Clip a ferrite on the fuel line.
3. Buy only from a reputable source, not ebay, etc.
4. Use lead-free fuel.
 

Offline tautech

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Re: Question about petrol/gasoline engine oils
« Reply #13 on: August 16, 2023, 09:09:00 pm »
For the most part I use full synthetic in all of my 4 stroke gasoline engines.   Even the small engines like my generator and such get it.  I think the generator requires changes after 5 hours of operation?
What brand would that be ?
Even decades old Briggs & Stratton engines only required 40hr changes.
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Offline Benta

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Re: Question about petrol/gasoline engine oils
« Reply #14 on: August 16, 2023, 09:58:16 pm »
Even decades old Briggs & Stratton engines only required 40hr changes.
Are you guys kidding me? 5 hrs, 40 hrs oil change intervals???
What kind of miserable engines are these?
 

Offline tautech

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Re: Question about petrol/gasoline engine oils
« Reply #15 on: August 16, 2023, 10:06:43 pm »
Even decades old Briggs & Stratton engines only required 40hr changes.
Are you guys kidding me? 5 hrs, 40 hrs oil change intervals???
What kind of miserable engines are these?
Splash lube.
Silicon alloy bores with chromed alloy pistons running alloy conrods without main bearing shells.
They were made for decades and decades and when looked after would also run for decades.

Old Kohler engines although of cast iron construction specified similar oil change periods.
tautech in an earlier life twisted spanners on these things.  ;)
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Offline joeqsmith

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Re: Question about petrol/gasoline engine oils
« Reply #16 on: August 16, 2023, 10:39:18 pm »
Typo, I thought 50 but just looked up the Honda, 100 hrs or 6 months. 

***
I have a cheap Steele 3500W which also calls for an oil change at 100 hrs or 6 months.   

What brand would that be ?

I was using Torco T-4R with the methanol.  Currently using the Brad Penn with gasoline.   
The 15W-50 and 10W-40 are in my two street bikes.   

For the 2-strokes,  I was using Yamalube but now Lucas goes in everything.  When I was growing up riding dirt bikes, mostly I used Golden Spectro.   

***
I have an Ariens snow blower with a B&S motor.  Calls for every 50 hrs. 
« Last Edit: August 16, 2023, 11:48:58 pm by joeqsmith »
 

Offline Benta

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Re: Question about petrol/gasoline engine oils
« Reply #17 on: August 16, 2023, 11:36:22 pm »
Jeez, I didn't know.
Always used electric or manual garden tools myself.
I feel catapulted back into the 19th century.
 

Online IanB

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Re: Question about petrol/gasoline engine oils
« Reply #18 on: August 16, 2023, 11:56:07 pm »
Jeez, I didn't know.
Always used electric or manual garden tools myself.
I feel catapulted back into the 19th century.

I have also been an electric tool user. However, I have noticed that gasoline engines are vastly more powerful than typical electric motors. For instance, a 1 kW electric motor might output about 1 hp if you are lucky, whereas lawn mowers with tiny gasoline engines can produce 2 to 5 hp easily.
 

Offline joeqsmith

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Re: Question about petrol/gasoline engine oils
« Reply #19 on: August 16, 2023, 11:56:36 pm »
About the only electric garden tool I own is a hedge trimmer, and I run it off my gasoline generator.   I image that this is how the people in CA will side step the new laws.

https://www.gomaterials.com/blog/how-californias-gas-powered-lawn-equipment-ban-affects-landscaping-businesses/


Online IanB

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Re: Question about petrol/gasoline engine oils
« Reply #20 on: August 17, 2023, 12:01:54 am »
About the only electric garden tool I own is a hedge trimmer, and I run it off my gasoline generator.   I image that this is how the people in CA will side step the new laws.

If I understood correctly, the California ban applies to all small gasoline engines including portable generators. I think in future, portable generators will need to be battery powered  >:D
 

Offline joeqsmith

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Re: Question about petrol/gasoline engine oils
« Reply #21 on: August 17, 2023, 12:16:44 am »
About the only electric garden tool I own is a hedge trimmer, and I run it off my gasoline generator.   I image that this is how the people in CA will side step the new laws.

If I understood correctly, the California ban applies to all small gasoline engines including portable generators. I think in future, portable generators will need to be battery powered  >:D
Pretty sure there are many videos showing an electric motor driving a generator with a feedback path to drive the motor and enough left to run your house.  So no problem there.   

Our small 2-stroke Lawnboy mower is over 40 years old now.  I can't see moving to a plastic electric mower just yet and spend my time swapping batteries.   Hard to beat the power density of gasoline.     

Offline tautech

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Re: Question about petrol/gasoline engine oils
« Reply #22 on: August 17, 2023, 01:04:30 am »
For the 2-strokes,  I was using Yamalube but now Lucas goes in everything.  When I was growing up riding dirt bikes, mostly I used Golden Spectro.   
There are different lubrication requirements for 2 strokes if they are:
Air cooled
Water cooled
Marine cooled.

They each have a different lubrication spec for the heat ranges they operate within.
Run any water cooled 2 stroke oil in an aircooled 2 stroke engine at your peril.
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Offline Bud

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Re: Question about petrol/gasoline engine oils
« Reply #23 on: August 17, 2023, 01:06:48 am »
.   Hard to beat the power density of gasoline.   
I am sure your neighbors love the noise and stinking fumes.
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Offline vk6zgo

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Re: Question about petrol/gasoline engine oils
« Reply #24 on: August 17, 2023, 01:24:25 am »
About the only electric garden tool I own is a hedge trimmer, and I run it off my gasoline generator.   I image that this is how the people in CA will side step the new laws.

If I understood correctly, the California ban applies to all small gasoline engines including portable generators. I think in future, portable generators will need to be battery powered  >:D
Pretty sure there are many videos showing an electric motor driving a generator with a feedback path to drive the motor and enough left to run your house.  So no problem there.   

Our small 2-stroke Lawnboy mower is over 40 years old now.  I can't see moving to a plastic electric mower just yet and spend my time swapping batteries.   Hard to beat the power density of gasoline.   

I had one good petrol mower years ago.
All the others have been rubbish.
They overheat after a short period & you have to spend ages getting them to start after they cool down.

I could never afford a Honda, so ended up with Briggs & Stratton or Tecumseh engined things.
I have fixed, serviced & rebuilt all sorts of car engines, but for some strange reason, I have trouble with small engines.

I eventually gave up on them, spent the big bucks & got a Ryobi "plastic" battery lawnmower, & have been agreeably surprised.
It handles my overgrown backyard just as well as the petrol ones, & if it "bites off more than it can chew", the motor "stalls", but you just pull it back from the overloading vegetation, push the "go" control, & away you go.

The petrol engines would stall, decline to restart & flood if I insisted.
On a warmish day, by the time I ran out of fuel, they would usually be hot & again refuse to start, necessitating a prolonged cool down time.

With the Ryobi mower, when the battery goes flat, I just remove it, take an extended break until it has charged, slap it back in, & I'm ready to go.

If I were "flush with funds" I could have two batteries & never have to stop.

Interestingly, the petrol mower which worked properly was an old 1960s "Rover" with an Oz made 4 stroke engine of unknown provenance.

It also had, as was common in those days in this country, a starter handle with which you wound up a large spring, then folded the handle down & bashed it on the top to start.
It would deliver all the stored energy in the spring very quickly, spinning the engine up to speed fast, almost always starting properly.

All the later ones had those godawful "pull starts", which require you to brace the mower body with your foot & heave on the cord umpteen times, till it either starts, or you get heartily sick of it & go inside & have a coffee instead.
 


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