Does gear oil go bad?

06Rinker270

I have some gear oil that is 5 years plus old, maybe more.  Is it ok to use or should I buy new?  Also, my mechanic was talking me out of mercury gear oil, saying it has had problems in the past.  Drawing a blank on what he said was wrong with it.  Anyone agree or disagree?

Thank you in advance. 

PickleRick

Gear oil, oil in general wont go bad on the shelf.


I don't know of any issues with mercruiser brand oil but as with any oem oils they usually take bids on suppliers and many times there is an equal or better alternative.

Willhound

What he said. Oil in a sealed container won't go bad. Somebody may disagree in that additives over a VERY long time might start to separate but would be at a microscopic level. Only problem is if moisture gets in it but you'd see that.
Mercruiser doesn't produce oil. Whoever got the contract for a particular batch refined it.

Michael T

Mercruiser is very specific as to who refines their products and the specifications for them. I'm not so sure about a petroleum product that is a half decade old for two reasons. Petroleum products do degrade over time (enough time) and newer chemical configurations are formulated to meet engineering changes. As an extreme example using previously formulated engine coolants when aluminum heads and blocks made their advent was not a good idea. There are lots of others. Question: For so little money - why take a chance on such a vital product that is IMO "old". ?

PickleRick

Gear oil hasnt really come a long way in the past 5 years...the last 20, yes.  

I wouldnt use 1985 Quaker state oil


But 2005 mobile one, toss it here.  

I have some old unopened Texaco metal cans from the 70s

Dream_Inn

5 year old unopened gear lube will be fine.

FWIW, I've always used high performance mercury gear lube.

Michael T

......only synthetics here - when available, although all automotive/marine oil in N.A. has some synthetic in it or it wouldn't meet EPA standards.

Aqua_Aura

Here is a good video on oil. This guy has all sorts of really good testing and comparison videos. Highly recommend watching them, I know you all have time 😁

https://youtu.be/-zHlxeu_yuM

PickleRick

Conventional oils have come a long way in being much cleaner, less impurities since the 90s 

I do like synthetics but i prefer blends.  Synthetic is better for bearings/journal surfaces. Conventional motor oil is better for seals/gaskets.  

Black_Diamond

Synthetics are completely compatible with oil seals and gaskets. You will find oil seals not compatible with some oils rated EP/AW though. 

Synthetics do flow better than straight mineral oils at all temperatures, that can lead to weeping of paper type gaskets and if the seal lip or journal surface is worn or damaged, they can get past the seal lip and leak. 

Michael T

.....and we have had so much fun with this topic over the past years. There is also the slam dunk advantage to synthetics regarding reduced start up friction (a big issue for many marine engines due to periodic use) and the massive advantage of friction reduction during internal temperature spikes even if for milliseconds a period in which other oils simply vaporize. If using full synthetic I do recommend a synthetic oil specific filter which has a number of the oil characteristic features in mind such as a much lower micron rating.

06Rinker270

I appreciate all the tips.  I have some left over and was curious if it was worth keeping for back up for get rid of it.  I will keep it as a back up and use new for this year.  Lets just hope the new stuff arrives on time!

PickleRick

For newer engines that call for synthetic go full synthetic.  It's all i run in my tdi and all i ran in my LS/VTEC turbo Honda i built years ago.

As for older vortec/350 engines and the like i prefer  blend.  They are more prone to weeping oil but still need the restart lubrication of the synthetics. 


My excursion has 235k on the clock, only ever ran dino rotella.  

Zero gunk under the valve covers, changed every 5k.  

Whenever possible i run dino rotella in anyting i own, i even run the same t4 15w40 in my rinker as i run in my excursion.  Also ran it on every motorcycle ive owned from a 75 cb550 to a 2006 Ducati monster.  Wet or dry clutch didnt mattrt.

I did go big and buy castor oil 15w40 synthetic blend for the rinker this winter because it was marked down to 18 a gallon.  T4 rotellla is usually 16.99

69fastback

Frequency of changes, and general maintenece will always be more important than brand and/or conventional/synthetic. 

06Rinker270

Great point @69fastback

Michael T

I respectfully disagree. 

I can't remember how long ago I posted the results of - at the time - true dino oil - that is with no synthetic in it - but in super high temperature situations......which most engines encounter at some point, the dino oil just vaporized.

Every time the "old" dino oils were run hot in an engine they lost return viscosity and ability to provide shear protection. After a few cycles of this you might as well have had dishwater in your engine.

Newer "dino" oils had to have some synthetic added to them to meet EPA mileage requirements and were a bit safer but no where near a quality semi or full synthetic.

As well even the lowliest synthetics smoked the best dino oils in friction tests. This testing was done on a dozen top brands by the Shell Oil labs and other forum members at the time sent in similar reports from some independent labs. 

So, no matter how many times you change an inferior oil product you are still using an inferior oil product. For boaters I would say that is just like shuffling the deck chairs on the Titanic. For gamblers I would say that no matter how many times you shuffle a hand full of deuces you still have a hand full of deuces.

So at the very time your engine needs protection you have an inferior product unable to protect it and we haven't even begun to discuss the long term benefits of friction reduction at start-up, anti-friction protection under load and longevity.

I respect all opinions but as a former teacher of advanced chemistry and physics in high school it is just not true to say that dino oil is equal - in ANY way, other than price to synthetic oil.

In fact synthetic oils ramp-up protection as engine conditions deteriorate in an overheat condition or even a spike as they form more comprehensive chain polymers when threatened by high heat - just as they were formulated to do.

Opinions are personal, facts maybe less so.

But my over riding question is  - given the cost of engine/drive repairs why would saving a few bucks on oil even be a consideration? To be honest that comment just baffles me!

69fastback

I still have never seen an engine failure that could be contributed to running Dino oil. And furthermore, I’ve never seen a failure that had an engine, transmission, or any other component that would have been saved, had it been running synthetic. If people want to run synthetic because it makes them feel better, then great, run synthetic. Just don’t feel like you’re doing your engine any disservice by running Dino oil. The main key is regular changes and maintenece. Mechanical components survived a long time before synthetics came around. 

I don’t run synthetic in my race car, for a variety of reasons. It does get changed after each night of racing, but it would get the same if I ran synthetic. I’ve torn down a whole lot of engines in my years of abusing them, and I’ve ran a lot of oils. At no time could I see any measurable difference in wear in the actual engine. 

PickleRick

I have seen engine failure due to dino oils.  2 cycle engine failure.  To meet new EPA standards some new 2 cycles (shindaiwa, echo) need to run synthetic or synthetic blend mix oil as the temps spike and conventional oil simply breaks down and allows metal on metal friction.

 In newer gm motors they run approx 210 to 220 degrees.  In raw water cooled boats 140 to 160 degrees.

Your engine oil will be approximately the same temp as your coolant.

I've yet to see a 4 stroke engine die because of oil failure.  Even in a mower running sae hd 30 that hasn't been changed in 3 plus years. All they do is top it off the level.  

Dino oil may burn off more quickly than full synthetic but if you're adding more than a quart between 7k changes on a gas motor you have a leak or an internal issue.  Some vw/audi engines drank oil between changes and it was a design flaw.  Not all engines are designed well, switching to full synthetic can be used as a band aid in some situations.

Under normal every day use (even racing) the oil should never get hot enough in a 4 stroke to break down with proper service intervals.

69fastback

Exactly what process did you use to determine that the failure was due to a Dino oil? I run Maxima 927 in all my 2 strokes, and I run those 2 strokes hard. 

PickleRick

Cylinder scoring only present on exhaust side of cyl/piston paired with a passing leak down test is a good sign of oil break down.

Different brands use different dye in their mix oils so many times a little visual inspection can tell you what's up before you dig in.  

Echo/shindaiwa tech support will tell you running orange stihl mix is a no no.  Stihl xp is not officially approved but the warranty techs i have to seek approval on for all warranties give an unofficial A ok.

Michael T

......please remember that no coolant can protect an engine from a temperature flare. Coolants are "general" protection during normal operating conditions as are low cost oils. Synthetics protect against potential damage that conventional oils are completely incapable of doing. What part of vaporization due to temperature flare is not understood? Again, I'm perplexed - happening more frequently at my age - but what does the difference in up-grading to synthetic cost, a case of beer????????

69fastback

Michael T said:

......please remember that no coolant can protect an engine from a temperature flare. Coolants are "general" protection during normal operating conditions as are low cost oils. Synthetics protect against potential damage that conventional oils are completely incapable of doing. What part of vaporization due to temperature flare is not understood? Again, I'm perplexed - happening more frequently at my age - but what does the difference in up-grading to synthetic cost, a case of beer????????

Now I’m perplexed by your last sentence. I wouldn’t always consider it an “upgrade,” as that’s debatable for certain applications, but did anyone here ever say not use synthetic, as that sentence implies?  

As I said, maintenece will always be more important than what oil you choose to use. Choose whatever you want, but engines don’t fail because someone used Dino oil.  

69fastback

PickleRick said:

Cylinder scoring only present on exhaust side of cyl/piston paired with a passing leak down test is a good sign of oil break down.

Different brands use different dye in their mix oils so many times a little visual inspection can tell you what's up before you dig in.  

Echo/shindaiwa tech support will tell you running orange stihl mix is a no no.  Stihl xp is not officially approved but the warranty techs i have to seek approval on for all warranties give an unofficial A ok.

That’s also a sign of poor jetting. If it’s lean, it’s not at fault of Dino oil, regardless of if synthetic would have add a slight bit more protection. Again, I’m not saying synthetic is bad, because it’s obviously not. I’m saying that if you properly maintain your equipment, the real world benefits of synthetic are nil. I run synthetic in my truck, and in my TE300i (because that’s what the manufacturer calls
for and it keeps the power valve cleaner), but I run Dino in some of my stuff too. Maintenece is more important. 

69fastback

Again, to be VERY clear. Nobody here is saying not to run synthetic oil. 

PickleRick

69fastback said:

PickleRick said:

Cylinder scoring only present on exhaust side of cyl/piston paired with a passing leak down test is a good sign of oil break down.

Different brands use different dye in their mix oils so many times a little visual inspection can tell you what's up before you dig in.  

Echo/shindaiwa tech support will tell you running orange stihl mix is a no no.  Stihl xp is not officially approved but the warranty techs i have to seek approval on for all warranties give an unofficial A ok.

That’s also a sign of poor jetting. If it’s lean, it’s not at fault of Dino oil, regardless of if synthetic would have add a slight bit more protection. Again, I’m not saying synthetic is bad, because it’s obviously not. I’m saying that if you properly maintain your equipment, the real world benefits of synthetic are nil. I run synthetic in my truck, and in my TE300i (because that’s what the manufacturer calls
for and it keeps the power valve cleaner), but I run Dino in some of my stuff too. Maintenece is more important. 

It's not bad jetting.  Its factory set aka EPA violation to mess with carb settings or even remove limiter caps.  Its the engine running leaner/hotter than older 2 cycles to meet current EPA standards.  Synthetic or synthetic blend is required to keep from scorching a brand new 591...but what do i know... I only do warranty work for them and do my required yearly factory service school updates which revolves around new EPA mandates as well as how it affects our service industry.    

I've only seen this issue in the 591, 600 and a few blowers.  

My info comes directly from warranty/tech department of my regional factory distributor.

PickleRick

I should note these are all brand new pieces of equipment with 1 or two uses.   My sales men were not paying attention to the new oil mix needs and sold a few with stihl orange mix oil.  Zero chance for it to be a carb issue and if it was a customer would report bogging before she locked down or in the event of a sudden air leak shed scream wide open before locking down.  All customers had propper mix ratios, one had a brand new ms201t he bought with a 600 and had to finish the job with the 201 after the 600 died.  

I put a new top end on each one with zero adjustments or repairs to the fuel system aside from pressure testing the fuel hose.

I eliminated all other possible causes before submitting warranty, which is what im required to do if it's Briggs and stratton, kohker, husqvarna, hydro gear, stihl or shindaiwa. 

Michael T

Totally disagree.....stating that "maintenance will always be more important than what oil you choose to run" just defies chemistry, physics and logic. No matter how often you change cheap oil you're still shuffling deuces. Think we said all of this years ago.

69fastback

Michael T said:

Totally disagree.....stating that "maintenance will always be more important than what oil you choose to run" just defies chemistry, physics and logic. No matter how often you change cheap oil you're still shuffling deuces. Think we said all of this years ago.

So all those engines before synthetics defied chemistry, physics, and logic????? Weird. And the engines that still survive on it today???  I have a motor that makes 2000 hp, and turns 9800 RPMs that runs on VR1. Maintenece is key. 

Have you ever had an engine failure that you could attribute to oil? Have you ever ran an engine in a max effort scenario and torn it down frequently to monitor its condition? Or do you just read the internet a lot?

69fastback

PickleRick said:

I should note these are all brand new pieces of equipment with 1 or two uses.   My sales men were not paying attention to the new oil mix needs and sold a few with stihl orange mix oil.  Zero chance for it to be a carb issue and if it was a customer would report bogging before she locked down or in the event of a sudden air leak shed scream wide open before locking down.  All customers had propper mix ratios, one had a brand new ms201t he bought with a 600 and had to finish the job with the 201 after the 600 died.  

I put a new top end on each one with zero adjustments or repairs to the fuel system aside from pressure testing the fuel hose.

I eliminated all other possible causes before submitting warranty, which is what im required to do if it's Briggs and stratton, kohker, husqvarna, hydro gear, stihl or shindaiwa. 

So the difference between Dino oil and synthetic is temperature based. What do you suppose the temperature difference is?  You believe these manufacturers would manufacture their tolerances to be dependent of that slight of a temperature from being okay to total failure?

69fastback

Hey but thanks for listing all of those brands, because if the difference between working and blowing up is synthetic vs Dino, then I know what junk I don’t want to own because that’s absurd. 

Really, my truck calls for semi synthetic. If I ran Dino, don’t you think it’d blow up??   Nope. That stuff you’re working on must be real junk. If the only difference between blowing up, and not, is Dino vs synthetic, then those turds are on the verge all the time. 

PickleRick

Dude, you can run whatever you want.  


Back in the 70s and 80s 2 cycle mac, poulan and homelite saws all ran 16:1 and you mixed 30wt motor oil with the gas.  Today's 2 cycle engines run much hotter and instead of 6000 max rpms they can run 10,000 or more.  How well would your truck run at 10,000 rpms non stop for 24 hrs straight?  Well a 179 dollar ms170 is rated to do that for about 125 non stop hours.  

Things change @69fastback

Across the board, all newer (past 3 to 5 years and newer) major brand 2 cycle equipment will last longer if you run synthetic or synthetic blend oils rather than dino oil.  The biggest killer of a 2 stroke air cooled engine is heat.  

Calling echo/shindaiwa junk because you need proper rated oil is a very ignorant statement.  Our 7.3 power strokes are not junk because they require specially rated oils to prevent gumming of the injectors.  My tdi isn't junk because conventional oils will lead to round lobes on the cam shaft (PD engine) synthetic only on a PD engine and some will say only vw rated at that but i like my t5 just fine.


Im sure you are just trying to get a rise out of me but your statement is extremely misleading and could lead someene who reads to ruin a piece of equipment or sway them away from a smarter purchase choice.

Your truck is liquid cooled and your rpms dont turn what todays air cooled 2 cycles turn.  You're trying to compare apples to oranges.  They are both internal combustion engines, that's about where the similarities stop.


I don't know the egts of a 2 cycle.  I do know the carnage caused by using improper mixing oil.