# Should you choose Synthetic or Conventional oil?



## kaptain_zero (Jun 2, 2018)

This is a fairly common debate and the choice YOU make should depend on what YOU think is right for YOU. Do not trust ME or anyone else to decide FOR you... make up your own mind, doing your own research.

Personally, I use both types of oil and I select them based on what I see as the important features for the equipment I have and my intended use.

Synthetic oil is frequently thought of as superior, longer lasting and better lubricating, and often expensive, I think it pays to dig a little deeper.

It is thought to be superior in part because it is engineered. It is a synthetic stock lubricant and will have a set viscosity. For the purpose of this B(rain)F(art), I'll pick 10w-30.

So the synthetic 10w-30 will have a viscosity of 10 when cold and as a synthetically created oil is pure, it will be all 10 weight, which is unlike a refined oil that might consist of some very thick, some medium thick and some very thin oils, that, when mixed together, comes out to the same 10 weight viscosity. The issue is that the thinner lighter oils tend to "boil off" easier or faster, allowing the oil to thicken in use. But, this is taken into consideration when the engineer sets the oil change shedule for that particular motor, so the oil is changed well before it gets too thick.

The synthetic oil, being all 10 weight, will thicken slower and thus we have the claims of longer times between oil changes.

Note however, the engine manufacturer will specify the oil change interval, regardless of whether a synthetic or conventional oil is being used, so to keep your warranty intact, you MUST CHANGE YOUR OIL AT THE MANUFACTURERS SPECIFIED INTERVALS, no matter what the oil manufacturer says. Once the warranty is past it's best before date, you may of course decide to extend that period between changes, but there are engines that would not take kindly to that. I shall elaborate later.

What about that 30 weight viscosity?

Both types of oil add a polymer additive to boost viscosity when the oil gets warm. Imagine a short filament (too small to be visible to the naked eye) that balls up when it's cold, but relaxes when it gets warm, unrolling into a longer filament. This is what allows the oil to behave more like a 30 weight oil when it gets warm. Some designs, such as typical motorcycle engine/transmission combinations, use the motor oil to lubricate the motor and transmission, the transmission gears tend to shear the polymers into shorter bits and this can manifest itself as a sticky gearshift, which is a sign that an oil change should likely be done. If it's only the engine that is being lubricated, there is no feedback to the operator, so one needs to follow the maintenance schedule.

Synthetic oils do, on average, flow better at cold temperatures because all the oil is the same weight/viscosity. This can be important in some situations... less in others.

I could go on, but I'll cut to the chase.

I use synthetic oils in two engines, my car and my snowblower. I use it for two reasons, one is cold flow.... both my car and my snowblower are operated in the cold winter... -40 is fairly common and conventional oil gets very thick at those temperatures. The other reason is that modern car engines have many advanced features such as variable cam timing and such, not to mention turbo chargers. They need lubrication, through small orfices, and they need it as soon as the engine starts. This to me makes a clear case for the synthetic oil's advantage.

My lawn mower, pressure washer and such, are only operated in warmer weather, when conventional oils flow just fine. Small engines often use a simple splash lubrication with no oil pump or filter, relying on oil changes to remove particles, grit and dirt. A synthetic oil would be fine, but it is more expensive and would have to be changed just as often as a conventional oil to remove those contaminants as there is no filter in the system to filter them out. In this case I feel that conventional oils are a good, inexpensive choice.

As for synthetic oils making an engine last longer..... perhaps they do, but will you still own that engine when it's 35 years old or will you have replaced it because you got bored of it, or something better came along? If you are no longer the owner, why would you spend the extra money to benefit someone else?

Check your owners manual and follow the recommended oil change interval and use the correct oil viscosity and API service classification. The API letters go from AA to ZZ and as oil improves and designers demand more from the oil, the designation goes towards the ZZ. You can safely use a later classification as it meets all earlier requirement AND the additional new ones. The oil manufacturers MUST provide samples of their oil for testing before they are permitted to put that API rating on their product, so you can trust it meets or exceeds the requirement for that rating.

And lastly, I see testing done on various oils using the industry standard 4 steel ball test and measuring the wear after a specified time. The problem I have with such tests is that nowhere in an engine do you ever have this kind of a wear situation.

When I started out decades ago, there was a company who made oil additives who came around to the repair shops and they would coat two heavy screw driver shafts, one with just oil and one with their additive mixed in.... you could hold the one coated with just oil between two fingers, but the one with the additive would slip and fall to the floor. An impressive demonstration, but nowhere in an engine will you find human fingers trying to hold the shaft of a screwdriver, so the demonstration was of no practical value.

So it pays to do your own research, think about how you intend to use a device. Is it something you want to try and make last forever? Will you be operating it in severe conditions? Will it be under a constant heavy load or will it be loafing along most of the time? Then look at both types of oil, their advantages and their cost and make YOUR decision... Not because Putrid Pink or Grimy Green oils are known to be the "best" and cost the most not to mention all the cool kids tell you to.


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## TheTurfTamer (Aug 8, 2018)

I am an equipment professional with Kubota in Huntsville Alabama. Everyday I seen very little issues in my service department with oil choices. Off road use equipment. Our number one selling oil is 10w30 and ISO AW 46( zone 8). I see problems everyday with fuel choices and fuel additives but none with oil choices.


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## ken-n-nancy (Jul 25, 2017)

kaptain_zero said:


> This is a fairly common debate and the choice YOU make should depend on what YOU think is right for YOU. Do not trust ME or anyone else to decide FOR you... make up your own mind, doing your own research.
> 
> Personally, I use both types of oil and I select them based on what I see as the important features for the equipment I have and my intended use.


Thanks for providing the good article. Lots of great information and a good perspective.

think the above conclusion -- that the choice of what oil to use is a combination of an engineering, fact-based decision, which may have different "right answers" for different types of engines, oil filtration (or lack thereof), usage scenarios, planned longevity, etc., as well as a personal (emotional / value-based) decision, which means that each person needs to make up their own mind and can, depending upon their circumstances, come to different "right" answers -- is a good conclusion.

I would also add that the situation gets even more complex, as there are a few number of synthetic-conventional blend oils out there, many of which are even used as OEM by automobile manufacturers, which go even further to muddy the picture. I actually such an oil in my automobile engines.

For people who really want to maximize their oil life and/or get additional insight into what's happening in their engines, there are oil testing services available. Personally, I use Blackstone Laboratories (https://www.blackstone-labs.com/) and have become confident of using extended oil change intervals of about 9K miles in my cars, based upon actual test results from my oil changes, based upon the actual engine wear, driving conditions, filtration systems, oil type, etc., for our vehicles as my family drives them.

For what it's worth, I use a synthetic/conventional blend oil in my automobiles and a straight-weight oil in the lawn mower.


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## ForsheeMS (May 21, 2018)

To my knowledge there is only one brand of oil to avoid at all costs and that brand is No Oil. That stuff is guaranteed to cause catastrophic engine failure! :lol:

Seriously, the majority of oils out there work fine provided the engine they are used in is in good working order and the change intervals match the type of use and environment they are being used in. A big part of any engine oil is the additive package and to me that is possibly more important than the base stock.

With that said, I do use synthetics in all my equipment and vehicles. Air cooled engines can be harder on the oil since engine temps vary so widely and are affected by the outside temps. Yes, it's probably overkill but it makes me feel so much better.


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## kaptain_zero (Jun 2, 2018)

At least 3 people bothered to not only read, but comment! Yaaaa :mrgreen:

@@Aawickham78 That's what I found as well.

@@ken-n-nancy it's been close to 40 years since I swung wrenches on tractor/trailers and back then we also sent out oil samples for analysis. But, we sent them out looking for a sudden increase in contaminants and based on what that contaminant was, we could perhaps catch a bearing or bushing in the process of failing, allowing us to pull that piece of equipment off the road and preemptively repair it before a catastrophic failure somewhere on the highway, delaying what was being shipped AND requiring expensive towing to a shop where we had to pay full price for the repair.

The use of lab testing to estimate oil life is an interesting one, but considering the cost, it seems to be a costly way to save a few $$$. My other concern, and this goes back to when synthetics became available, was the claim that synthetics would minimize the buildup of contaminants in the oil, and thus last longer. I thought about it for a while and then started to wonder where all the combustion byproducts went, if not into the oil? Are they going out into the exhaust system where those contaminants such as acids wreak havoc inside that system?!?! I don't know what the answer is, I'm just following the bouncing ball in my own puny little mind (which does seem to go off the rails more often than I like).

@ForsheeMS Indeed, if cost is not an issue, using the correct grade synthetic oil is fine... it may not do the job any better than a conventional oil in some cases, but it won't do a worse job, as long as it meets the correct API classification.

You are also correct about additive packages, and these are necessary to meet the API classification that the manufacturer wishes to sell their product under. As such, some meet the specifications and other manufacturers exceed the specifications. I suggest to anyone interested, to swing by https://www.api.org/ where you can find a list of manufacturers who have had their products certified and how well they did. (unfortunately, I don't know exactly where on that site that you can find it as I have not looked in some time).

As for air cooled engines, being an old fuddy duddy, I tend to divide air cooled engines into two groups. What I call "air cooled" which I call things like motorcycle engines (think Harley Davidson) and fan cooled engines like a Briggs & Stratton lawn mower engine. The passive air cooled engines rely on air from moving to wash over the cooling fins and they can indeed develop hot spots, but a synthetic oil is not going to save that engine from damage. If something happens, it's usually a piston that expands too much vs the cylinder an starts to bind until it seizes. Today's well designed engines rarely run into that problem. Fan cooled engines (as long as the air intake isn't blocked by leaves or grass clippings) are more reliably cooled, and again, any excessive heat buildup damage would not be prevented by one oil over another. In this case, selecting one oil over another to prevent this sort of damage is likely pointless.

And a quick warning about single weight oils.... No, there is nothing wrong with using say a 30 weight oil over a multi grade oil..... BUT.... there's always a but somewhere, be careful when you purchase your 30 weight oil, some of those oils are what I call "machine oil". Machine oil is used for lubricating things like lathes, milling machines, drill presses and other such things that do not have a combustion engine. If using in a combustion engine you must have detergent additives in the oil which are actually detrimental if used for machines that don't need them. The safe thing of course is to just make sure it has the appropriate API classification for your engine and then you know you have the right oil.

Personally, I use a multi-grade oil, 10w-30, even in my lawn mower, and that is because in my neck of the woods... it gets bloody hot in July and August, but it can get close to freezing in May and September.


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## Shindoman (Apr 22, 2018)

Good read. 
Conventional oil has worked great for many many years. That's what I use in my mower and power edger. Full synthetic in my dirt bikes and all my cars where there I believe the higher rpm's will require the best protection possible.


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## William (Oct 2, 2017)

Initial oil is conventional on new equipment. For first oil change I move to synthetic. If I buy a used item, I just use conventional. Generally I am a SAE 30wt. Guy.

Not necessarily related, but I have bought a few boats new with 2 stroke outboards. The general consensus is the oil you use on day one should be the same oil you use on the day it blows.


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## kaptain_zero (Jun 2, 2018)

I remember when they first started with synthetic oils and they were not compatible with conventional oils.... that was very short lived and today you can use either and switch back and forth between the two or even mix them together, if you wish, with no worries.

As for using the same brand from day one on..... a nice sentiment, but at times impossible to do, and you might not even be aware that something has changed.

I take my car to a friends shop as I can't be bothered to get dirty anymore, when it comes to my car. I asked what was up as the oil brand changed from my usual brand of 8+ years. The answer was that it was exactly the same oil. The company that made the oil, bought another company whom the original company made the oil for. The manufacturer decided to use the purchased company's container and name as it had a larger market share. There is so much of this branding going on, it's hard to keep track if you don't know someone on the inside. The other tidbit I got from him is that now, they ONLY use synthetic oil and the price they get it for, is identical to cost of conventional oil. They figured that with 7 months of cold weather each year, there's no harm in using an oil that flows better in the cold.


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## thesouthernreelmower (Aug 28, 2018)

Great post. Also I hardly ever see anyone talking about air filters. A dirty air filter, one that lets say a grain of sand into the engine, is far more damaging to the cylinder walls than a "lesser" quality oil.


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## HomerGuy (Jun 5, 2017)

I recently starting using full synthetic in everything. Vehicles, mower, snow blower, etc. The cost of synthetics has really come down and they don't command as much of a premium as they once did.

It seems like Mobil 1 or Pennzoil is always running a rebate on the 5 qt jugs. I think Mobil 1 is $23 for a 5 qt jug at Wal-Mart, and with a $10 or $12 rebate the cost is super cheap, oftentimes cheaper than a conventional.

I agree that full synthetics are likely overkill in many applications, but cost is becoming less of a factor in the choice.


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## MasterMech (Sep 24, 2017)

-I'm deleteing the first part of my post because I am guilty of not reading each of the OP's replies in this thread. And for that, I apologize.-

While I agree that synthetics hold little financial incentive for their use in small engines, especially over conventional oils labeled to meet the same standards, I passionately disagree that the use of a synthetic oil does not benefit the engine or its owner. Also, while automotive oils are still quite adequate, there are engine oils formulated specifically for off-highway applications that address the needs of these engines far better than the latest automotive oils.

And as far as not caring about the next guy that may own that engine, well, that's a pretty shitty attitude to live by if you ask me. If you can't/don't want to make repairs to older equipment or need/want to upgrade, pass on your older, well-maintained equipment knowing that you may have blessed someone else with it rather than dumping your problems/ignorance on them.


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