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oil change; hours or calender?


Pilot Dane's Avatar
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04-15-14, 10:07 AM   #1  
oil change; hours or calender?

I have a couple pieces of equipment an old compact excavator and tractor front end loader. The manufacturers recommend 250 hour oil changes but these machines may only get 30 hours run time a year. When would you change oil?

Both are diesel powered. They are stored inside a temperature controlled garage so condensation and rust is almost nonexistent. They are run/used at least once a month for an hour or so so the oil gets good and hot and the cams & crank can stay oiled to prevent corrosion. Both are over 10 years old and far from new so there's no warranty to worry about. Still I hate changing oil annually and see good looking oil get poured out.

 
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04-15-14, 12:07 PM   #2  
Neither my tractor or 4x4 truck get enough hours/miles for an oil change in a years time but I change them every yr anyway. I'd rather be safe than sorry. If I wanted to save money, I'd probably drain a couple of quarts and replace it with fresh oil.


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04-15-14, 05:40 PM   #3  
I'm an every year man too. Just before the cold season with that type of equipment.

 
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04-15-14, 06:39 PM   #4  
I'm not. Oil doesn't just sit there and go bad. If it's clean, run it. Most folks dont hesitate to use oil that was in a bottle on the shelf in their garage for 5 years, but they think the oil that sat in their engine for a year barely used must need changing. The only thing it could do is possibly collect a tiny bit of moisture. This will be insignificant and if you run the equipment to operating temp once in a great while, this won't even be a consideration. It will cook out as vapor as soon as the engine gets warmed up anyway.

I change my oil when it looks like it needs changing. If it's 100 degrees, super dry and dusty, and you're working the engine harder than usual, it might need an oil change twice as often as it would if it was cool, wet, and the engine was under light loads.


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04-16-14, 04:00 AM   #5  
I agree with Cheese. If I can't read the writing on the dipstick through the oil, I change it. Especially in my Cummins. Recommended change time is way too long for what I consider to be safe. If it is dirty, change it. Same with my Ford 640 tractor and Kubota ZD21.

 
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04-16-14, 04:30 AM   #6  
No, oil in a bottle or can sitting on a shelf doesn't go bad but the oil in your engine DOES go bad. It is contaminated by dirt, moisture and a little thing called acid as a result of the moisture and, heat and unburned particles of fuel. Even oil in equipment that isn't of the internal combustion engine type becomes contaminated and the acid content is what is important as it WILL over time corrode bearing surfaces. Oil analysis is the only way to be certain that the oil is suitable for continued use. Analysis will report on the amount and size of any particulate matter and also on the Total Acid Number (TAN) along with a recommendation to either continue using the oil or to change it. You can NOT tell if oil is suitable for continued use by just "looking" at it.

For the greater portion of my working career I worked in a facility that had several rotary-screw air compressors. These machines had two-stage air filters and full-flow oil filters and used a #10 weight automatic transmission fluid for sealing, lubrication and cooling. The largest machine was eight hundred horsepower (3000CFM per minute) and held 110 gallons of oil. Each oil change was approximately $500 for just the oil alone and then add in the costs for new filters, labor and oil and filter disposal and you can see that the lubrication side got rather expensive when we changed the oil every 2000 hours. We sent out samples every 1000 hours, or roughly every six weeks as the machine ran 24/7 most of the time. Since the test results always said the oil was suitable for use, even after 2000 hours, we started going to a 3000 hour change and that was when the wear particles, dirt particles and TAN started to rise to a point where change was recommended. I might add that these tests were done by the oil supplier so they had a vested interest in having us change oil more often. I'll also add that these compressors ran oil temperatures in the 210 to 130 degrees F. range.

Compare that to the largest air compressor, a four-stage centrifugal, that used a slightly heavier hydraulic oil for the gears and bearings but operated at about 130 degrees F. On this machine we NEVER changed oil which was also in accordance with the compressor manufacturer's recommendation. We DID change the oil filter occasionally if the pressure differential exceeded 10 psi. Note also that the oil was circulated in this compressor 24/7/365.

Now for the nitty gritty. The ONLY way to determine if oil is suitable for continued usage is via analysis. Unfortunately, the cost for analysis is often equal to or greater than the cost of changing the oil, including labor and disposal costs. The life of any oil is highly dependent upon the working environment. If the oil can be kept clean and the temperature below about 150 degrees F. the oil will have a very long life. However, temperatures above that point WILL cause the oil to break down. Moisture WILL eventually emulsify and in the presence of high temperatures WILL turn acidic. All oil used in internal combustion engines WILL become contaminated with unburnt fuel and also products of combustion. Engines that do NOT reach an oil temperature of more than 200 degrees F. WILL concentrate moisture in the oil yet running the higher temperatures will also cause oil breakdown so it just makes sense to change internal combustion engine oils more often than oil used in a non-engine machine. Since air-cooled engines run hotter than liquid-cooled engines it makes sense to change the oil in an air-cooled engine more frequently than in a liquid-cooled engine.

 
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04-16-14, 04:52 AM   #7  
I can't refute anything Furd says. But the practicality and reality is that for all intense and purposes home engine (not cars) appliances are not going to be harmed by little used oil sitting in the sump pan over the winter. Before that happens other mechanical areas will break or wear out having nothing to do with engine oil. I do as Chandler and Cheese for many years and have never had any ill effects due to oil. Today's oil far exceed engine manufactures required specs.

Now gas on then other hand is a whole new ball game as I have experienced in my riding mower. I need to rebuild the carb from scratch.

 
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04-16-14, 05:47 AM   #8  
Thanks for all the input. I know I'm over thinking this at least for the excavator. When I bought it there was a thick layer of mud in the bottom of the fuel tank and the hour meter was disconnected so it's probably getting better care now than at any other point in it's life.

 
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04-16-14, 05:49 AM   #9  
My post was a technical response to Cheese stating he simply "looked" at the oil to determine if it needed to be changed. As a practical matter, changing oil once a year, or once every five years, is probably okay for most home and garden engines. Far more important than changing the oil is making sure that the oil is at the proper level.

I don't have any IC engine powered equipment other than my automobile and haven't for at least a couple of decades except for my little generator which is fueled by natural gas or propane. The gennie only has 15 hours on it so I still haven't done the initial oil change recommended at 25 hours. I have owned air compressors since, well, forever, and I have never changed oil on one except during a major overhaul. I don't recall ever changing oil on a gasoline-engined lawnmower back when I had one. Heck, it has been over a year since I have had the oil in my car changed but I do not drive much these days but when I do it is usually a good half-hour or more at freeway speeds. I think I have averaged less than five thousand miles a year since I retired. "Looking" at the oil on the dipstick and it "looks" just fine. Same with the generator.

My personal opinion is that as a rule "we" (meaning everyone) change oil in our cars, lawnmowers, tillers and everything else more often that necessary. This is especially true of those that believe that line about changing the oil in your cars every three thousand miles. THAT is just so the oil change places can make more money. I have changed the oil in my cars at five thousand miles ever since I have owned a car and I have never had one that didn't far exceed 100,00 miles and even then the internals were clean as the day it was built. That doesn't mean that the oil "looked" clean as it surely didn't but color of oil is not an indicator of usefulness. Same with the air filters in a furnace, just because it "looks" dirty does not mean it needs to be changed. I've seen white air filters turn black in less than a week yet still have a very low pressure drop.

One more thing. I DO recommend changing the oil filter more often. Filters are generally less expensive than the oil so changing a filter between oil changes is a low-cost thing to do. When I was in college I was a work-study student and among other things I periodically changed oil on a Diesel-engined generator. Never changed the filters but changed the oil regularly and I think that beast took about five gallons (maybe more) of oil. When I questioned the supervisor about not changing the filters I was told to just do my job. These days I would be the supervisor and I would change the filters at least once and maybe as many as three times between oil changes.

 
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04-16-14, 09:43 AM   #10  
Thanks for the reply Furd. I know oil can be bad or sit and go bad after it has been contaminated in the engine. I'm talking about the case before us in this topic where the oil is new and just sitting in the engine for a while. It doesn't really go bad for a long long time. I don't have the experience with sending it in for analysis like you do, but I'm sure the oil will test just fine in cases where the oil still is clean like new oil. Even dark dirty oil can pass analysis. I just think that it doesn't make sense to dump several gallons of oil with only 30 hours on it because it has been in the engine for a couple years. It won't be bad in that time unless there is some undisclosed abnormal factor. Since we have to develop some method of determining how often to change our oil and we can't reasonably send in oil samples every time to check, this is the method that works for me.


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04-16-14, 11:44 AM   #11  
I actually agree with you. Whether a person changes the oil in the lawnmower, tiller or garden tractor in the spring or the fall is almost irrelevant. Changing it once a year or once every couple of years is unlikely to make much difference in the long run either. The one thing I will stress is to check the oil level at the beginning of the season and half way through the season because low oil (or NO oil) will be far worse than running oil with a few contaminants.

I think the cheapest oil analysis I ever saw was $16 and that was at least a decade (maybe two decades) ago. Even at today's ridiculous prices for oil a person would have to get a lot of use from the oil to justify the cost of analysis. I think that is why oil analysis has never been popular outside of industrial uses, it is just cheaper to change the oil than to test if it is still useable.

 
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04-16-14, 11:58 AM   #12  
A little OT, but when I was in the Navy...some guys would actually use the ships oil lab to get their auto oil tested to determine how long they could go before changing it. 1 or 2 tests over a period of time and they had a pretty accurate figure to go by.

Of course many newer machines probably have a idiot light that tells you its time. I know many high end vehicles do at least.

I changed my push mower every 2 years and kept it full in between. Cars I normally go 6000 or even more. Mine are driven enough to get to operating temps for 20 min or so, but are not abused. We also don't have any real moisture problems out here since the humidity is so low.


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04-16-14, 05:39 PM   #13  
We all seem to agree that frequent oil changes on home appliances is not necessary.

I do take exception to Furd's line about changing the filter and not the oil in a car. That is not a good practice. All you're doing is contaminating a clean filter that will plug up and then the engine uses a bypass valve to skip a clogged filter. A car is much too much of a precision machine and expensive item to play games on engine oil to save a couple dollars. I do believe and agree that those people who do a 3 or 4 thousand mile oil changes on cars are nuts. Today's cars and oils can easily go the 10,000 miles or more and if you use all syn it's even greater. Sever conditions (taxi service) requires more often changes at perhaps 5,000 to 7,000 miles intervals. But on a car always change filter with oil.

 
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04-16-14, 06:09 PM   #14  
I don't recall the exact numbers, but I recall hearing information about a test done with a vehicle (I believe it was a chevy truck with a duramax diesel) that was running on the same oil, having an analysis done at mileage intervals. The filter was changed every 5k and I want to say it racked up near 20k miles before analysis showed a need to change it. I don't remember if it was synthetic oil or conventional.

I try to change mine in my cummins every 7k or so (conventional oil...rotella) and I run synthetic in my nissan and try to change it about the same but sometimes I go a bit farther just out of neglect I suppose. Both are pretty dark by then. In my mowers and small engines, I try not to let it get black. Small engines run at much higher temps and the oil is less forgiving. Especially if using multi-weight. When it gets the color of a pitcher of strong tea, that's when I figure it's close to time to change it. It could go more I'm sure, but better safe than sorry.


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