Oil Change Frequency: How Often & Why?

[Pkruse]

How often do you change the oil in your personal car, truck, or other transportation device?

Why did you decide on that frequency?

Do you do anything out of the ordinary to extend the frequency? (Special oil and/or filter?)

 

[JonDE]

Every 5k miles. More then half my driving is done on freeways while not in traffic. It really isn't needed every 3k miles unless most of your driving is done on city roads or in traffic.
The only recommendation I have is not to use the super cheap oil. It doesn't last as long and doesn't protect your engine as well. A normal penzoil or whatever name brand you choose should be just fine.
I change my own oil, you can tell when oil has gone too far. If it comes out like molassess, its gone too far.

 

[Greg Bernhardt]

Go by the manual. I think winter and dusty environments will require slightly more often changes.

3k is usually given by the oil change places. Obviously they want you back in ASAP. Most new cars are fine with 5k intervals. I drive a recent Civic and go by 5k.

 

[Pkruse]

Here is why I asked.

In the commercial and industrial worlds, we have become very much aware that the OEM will always suggest maintenance intervals that are extremely conservative. I know of one aircraft component, for example, where the recommended service interval was 50 hours. But after a great deal of research and testing, the FAA bought into a 5000 hour frequency. Then with additional effort to continually monitor the actual condition of the component in flight, the frequency got pushed out to 50,000 hours, or whenever the monitoring instrumentation detected a potential problem.

That is how the development of “Predictive Maintenance Engineering” has developed.

Then the other day I was in the shop where I bring my car, when I saw an engine being torn down. It was in absolutely the worst condition I had ever seen. When they pulled the valve cover off, I saw a mass of carbon that looked like a valve cover. This was from a Toyota pickup truck owned by an auto parts store. They used it as a delivery truck, the worst possible service. They had never changed the oil, ever. Yet they drove it into the shop with a new motor in the bed and a little more than 400,000 miles on the odometer. The engine had finally lost enough compression that the owner decided it was time to do something with it.

So everything people tell me about how not changing the oil makes the old oil break down and do bad things is true. But it seems that the commonly assumed change intervals are extremely conservative. How much longer do you think this engine would have lasted beyond 400K before they would have had to replace it anyway, if they had changed the oil every 3K? How many of us would have kept the truck long enough for it to accumulate that many miles?

 

[AlephZero]

I don't undestand why US cars apparently have such short oil change intervals either. Many new European cars specify oil changes at 18,000 miles / 30,000 km.

The aircraft component life comparison is a bit misleading. Components may start with a short declared life because it would be too expensive, and take too long, to test them in realistic conditions. Even 5000 hours use would take one or two years to accumulate. Effectively the parts are tested (by regular inspection) while being used, and airlines may get paid for the inconvenience.

 

[xxChrisxx]

Defining by a time period for oil change is done purely to make things simple for people who don't have a clue.
It all depends on how the car is driven. More importantly, how many heat cycle the oil goes through and how much time the engine is run in cold (low lube) conditions. 3k miles is a carry over from the mineral oil days as they break down. With synthetic you don't have the problem.

I essentially only do motorway miles (so >90-95% of the time fully up to temp), I've not changed the oil in about 12k and it's happy as Larry going to over 20k without a change.

The only way to tell properly that you need to change the oil is to look at the oil level and the colour.

 

[Greg Bernhardt]

The only way to tell properly that you need to change the oil is to look at the oil level and the colour.

What color should it be when needing a change? Is there ever a time you can just add more oil instead of getting a change?

 

[jim hardy]

My Dodge van recommended every 10,000 miles to my surprise. So that's what it got.
I always used good oil never the cheap stuff.
It went 300,000 miles and engine was quiet & still clean inside when i gave it to a neighborhood youth.
Read the labels on back of can. I look for oil that says "Meets API XX" instead of "FOR API XX" but that's just me.

The API service letters start with a S or a C.
S means the oil was tested for Spark ignition engine(meaning ordinary gasoline engine) service
C means for Compression ignition (meaning Diesel) engine service.

I use API C rated oil even though it's not what the book says. But my rigs are all well beyond warranty.
Use what factory recommends until you're past warranty.
My reasoning is diesels with their 20::1 compression probably hammer the internal parts harder so need extreme duty oil. But I'm no engine designer.

I've had no troubles with 15-40 or 15-30 C oil in my vehicles even though book calls for 5-30 S .
Even in cold weather - my 92 Oldsmobile (small block GM V8) recently started fine at -25F (-31C). It had Shell Rotella 15-30 in crankcase.
My old van thrived on Walmart house brand fleet oil, C rated. It says "FOR not MEETS" but the van was expendable. And the oil passed my test.

An aside here -
i've also become a believer in changing automatic transmission oil every 50K miles. Otherwise they give up on me at about 150Kmiles.

old jim

 

[xxChrisxx]

As the oil traps and suspends un-burnt HC, soot, bits of metal etc, it'll become darker.
I change it when it has get's to dark chestnut.

But naturally this is really quite subjective. You'll find that different car owners will tend to converge on a rule of thumb.

http://img.wikinut.com/img/gwg477tc6hhng9ub/jpeg/724x5000/engine-oil-color.jpeg
On this scale mine is probably just after a 5, but not a 6.
Some might advocate a change at anything beyond 4.

 

[Pkruse]

I'm surprised that nobody had suggested actually testing the oil to see when it needs changed.

While I used an aerospace example of predictive maintenance, the practice is becoming common in the industrial world. I've seen similar results in elevators, cranes, and all manner of processing equipment.

As one example, I once managed a fleet of forklifts. These were gasoline, propane, and diesel engines. I extended the oil change frequency to once per year, but I monitored the oil condition by pulling oil samples regularly. Once I had enough data to know the trend, I cut back on the sampling frequency to also once per year, just before we changed the oil. We got a much longer service life out of our fleet than the industry average. When I left that job, some of them were more than 30 years old. We never once had an engine fail in anyway remotely related to the oil. In the thousands of oil sample reports I got back, I never got one that said the oil broke down, just that it was dirty, or sometimes wet.

 

[Pkruse]

I remember back in the early 1970's when I studied the API oil ratings, the "S" stood for "service station." It was said this was the cheap stuff sold in service stations, but was good enough for cars. The "C" stood for "commercial," and the testing standards were much more rigorous. Keep in mind that back then the trucking industry was still in the process of converting from gasoline engines to diesel. All the new trucks were diesel, but you still saw a lot of the old gasoline heavy trucks on the road. They used the "C" grade oil in those old gasoline engines as well as in the newer diesel engines.

But in modern literature, the "S" is generally said to stand for "Spark Ignition," and the "C" is generally said to stand for "Compression Ignition." This effectively divides them up in the same way, but somewhere along the line we seem to have changed the nomenclature a bit--though once in a while I'll still hear an old timer use the old nomenclature. I've seen oils with an "S" rating that had no "C" rating, but I've never seen it the other way around. Those that I've seen with no "C" rating have always been the cheapest oil available under some generic label.

 

[turbo]

I change oil and filter about every 7500 miles or so. My nearest drives are ~20 miles, so the oil has time to heat up well. Short drives in cold weather are not kind to engine oil - the water degrades oil.

 

[Pkruse]

Short drives in Florida weather don't do any good, either. I've seen large accumulations of water in engines that run for short periods of time. Any run that is less than about 25 minutes will leave you with more water than you started with. Then you need to start looking at the TAN number in your analysis, total acid number. Water plus acid is bad. That would call for either frequent oil changes, or the addition of a filter that takes out the water.

Oils have additives intended to capture and hold a certain amount of water. When those additives are over taxed, the oil will begin to turn milky in appearance.

 

[AlephZero]

Is there ever a time you can just add more oil instead of getting a change?

If you are burning that much oil, either you have a vintage car that burned and/or leaked a pint of oil every 200 miles even when it was new, or you need a new engine.

If you are changing every 5k miles, you should hardly need to top up the level between changes (unless you use a cheapskate garage that only fills up to the "empty" mark on the dipstick to make a bit more profit...)

 

[mrspeedybob]

In the commercial and industrial worlds, we have become very much aware that the OEM will always suggest maintenance intervals that are extremely conservative.

That is not true of OEM oil change recomendations. GM had a situation with the 3.6L V6 where the timing chains would wear out prematurely. Their solution was a reprogram for the ECM that caused the oil life monitor to count down more quickly. In addition they started specing their own oil for 2011 and later model engines. They call their new oil Dexos, it's basicly a synthetic blend.

Car manufacturers are under pressure from then EPA to produce cars that produce less polution. Used motor oil is part of that formula so manufacturers now try to specify only enough oil changes to keep the engine emisions compliant for the duration of the manditory emissions waranty.

Oil testing is a good way for industrial engine users to do fleet maintenance but is usualy not practical for individual drivers. The best advise is to look at the oil every once in a while and change it when it is dark brown or black. Use quality oil and a quality oil filter.

 

[Fahlin Racing]

Changing your oil, can't entirely be judged by color. IMO you have a better view when you look at the fuel mileage, engine operation (idle speed and above) and the color. I can always tell in my truck when my oil is due just by how it speeds up between new oil and spent oil. Sounding different as well. Being higher in miles, my rings are not keeping blow-by to a minimum simply because the oil is dark faster due to hydrocarbons. Obviously, city driving anywhere you will create stresses and more wear from starting and stopping than a vehicle that may drive over long distances, even with todays engines that use full synthetic oils. My truck just needs an overhaul.

An example of a long interval is the rear axles of some manfacturers in heavy truck etc stating with the pump and filtering system you can go 250,000 miles with this or that fluid. If you use synthetic over the blended viscosity you can run longer intervals, but, if you have performance applications street oils still don't qualify as a race oil in either realm and you will be changing the oil sooner than you would like. Bob mentions oil testing not something for the everyday commuter, sure you need to find somebody who can do it, I think it should be something to consider every 50,000 mile interval to just evaluate how your engine's health is throughout owning any type of vehicle.

I have used Castrol, Pennzoil, Valvoline, Amsoil. Valvoline broke down/became dirty faster than Castrol when I was evaluating in my Grand prix V6. If I remember correctly it was around 1000 miles sooner than Castrol even turned darker than out-of-the bottle color. I haven't used alvoline since then. I am using Pennzoil currently. I am thinking about if the high mileage oil is really worth the purchase, I am approaching 200,000 miles on my 5.2L Dodge Ram pickup.

 

[HowlerMonkey]

Cars are running the cylinder heads hotter and hotter with each year for efficiency reasons.

oil change frequency is related to these changes.

 

[Pkruse]

Lots of people have a favorite guess as to the best oil change interval, but nobody really knows unless the have their oil analyzed regularly. Lacking actual lab results, it is best to guess conservatively, and most do. Recommendations in the manual are very conservative. Your manual might say 7000 miles, but 20,000 might be completely reasonable for your car and its duty cycle, if you had the lab reports to back that up. I've studied thousands of reports for hundreds of vehicles. The data covered two and a half decades. Engines are hotter today, but the oil is better. It does not wear out. It becomes contaminated, and that is why we change it. I've seen an engine run four million miles with four oil changes, each due to a failure that put coolant into the oil. That Detroit series 60 has a very excellent aftermarket filter, which the owner changes every 10,000 miles. When he does, he adds makeup oil, which is sufficient to maintain the additive package. I never change my oil, but I change my filter every 10,000 miles. I use a filter that I know to be better than most because I've also run lab tests on that. My policy is to change cars every quarter million miles, and I've never had an engine wear out before that.

 

[Pkruse]

Adding detail to that last post:

Lots of people have a favorite guess as to the best oil change interval, but nobody really knows unless they have their oil analyzed regularly. Lacking actual lab results, it is best to guess conservatively, and most do.

Recommendations in the manual are very conservative. Your manual might say 7000 miles, but 20,000 might be completely reasonable for your car and its duty cycle, if you had the lab reports to back that up.

I've studied thousands of reports for hundreds of vehicles. The data covered two and a half decades. Engines are hotter today, but the oil is better. It does not wear out. It becomes contaminated, and that is why we change it. I've seen an engine run four million miles with four oil changes, each due to a failure that put coolant into the oil.

That Detroit series 60 installed in a long haul truck, a Peterbilt, has a very excellent aftermarket filter, which the owner changes every 10,000 miles at a cost of about five dollars plus two gallons of makeup oil, which is sufficient to maintain the additive package. I never change my oil, but I change my filter every 10,000 miles. I use a filter that I know to be better than most because I've also run lab tests on that. My policy is to change cars every quarter million miles, and I've never had an engine wear out before that.

It might be good to add a few words about oil filters. They come in two flavors. One is the less expensive full flow surface type filters commonly supplied by the manufacturer. The entire oil volume flows through it, and its filtering mechanism is similar to a coffee filter. The contaminant particles get caught at the surface, hence the name “surface filter.” From my experience in lab tests, they are very inefficient in catching particles smaller than about 30-50 microns. They also do nothing to take out the water.

The second type of filter is a bulk or "depth" type filter, and it is commonly installed in a bypass or “kidney” loop. It takes a small part of the oil flow, filters it extremely well, and returns it to the sump. Think about flowing your oil through a bale of cotton. Some larger particles will be captured on the surface, but most the smaller ones will be caught somewhere inside of the bale. These can’t handle the great amount of flow that a paper surface filter can handle, as the fluid flows through them more slowly. That is why they are set up in the bypass mode, and they are very effective at pulling out particles down to one or two microns. They can also be designed to pull the water out of the oil through absorption into the filter media.

Bypass filters are becoming very common on industrial and commercial diesels. I bought a number of generators with Cummins diesels in them that advertised an increase in oil change interval from 100 hours to 500 hours. They came with a spin-on filter cartridge with two sections, a full flow and a bypass filter in a single container. By adding a supplemental bypass filter offered by Cummins I could increase the interval to 1000 hours. My lab tests showed that these interval estimates by Cummins were extremely conservative.

I once added the same type of filter as that Peterbilt owner used to a 650 kW generator with a Cat diesel. I pulled an oil sample before adding the filter, and that came back three times dirtier than my threshold for changing oil, but I left the old oil in it anyway. I pulled another sample after running it for one shift, and that sample came back cleaner and dryer than new oil in the drum. The TAN (total acid number) had dropped to nearly zero. Since this engine was twice as big as the one in that Peterbilt, I actually added two of the filters in parallel instead of one.

Perhaps something should be said about water in the oil. One of the more important additives in oil is an emulsifier that keeps water in suspension, such that you cannot see it by visually or physically examining the oil. The oil can hold a great deal of water without you knowing it. But when the oil reaches its limit, the additives can absorb no more and the oil becomes milky. By the time you have enough water in your oil to see it, it is possible that damage has already been done.

If you can keep your oil dry, then the acid in it can do no harm. The acid needs water to be acid. When people talk about additives depleting in oil, the one additive that depletes the fastest is this water absorber. If you can keep your oil dry, then you don’t need that additive and that additve will last pretty much forever, and all the other additives commonly last much longer anyway. All this is based on my experience in Florida, which is a very wet place to operate an engine. You may get different results if you live in a dry place.

The bypass filters keep the oil extremely dry, which is one reason these engines last so much longer. When I said that the Peterbilt owner changed his oil four times in four million miles due to coolant leaks, he found those leaks by oil analysis before they became big enough to be serious. The oil had not yet become milky. The lab reports came back not showing a presence of water, which the filter takes out, but showing instead the presence of elements common to antifreeze and not oil. He can monitor many possible failures by understanding the lab reports from the samples he pulls at every filter change.

 

[Fahlin Racing]

What is your view on the breakdown of the viscosity improvers or 'additives' that are the reason we change our oil? Even if we filter it thoroughly and continous, how much does this longer oil life show as far as the multi-viscosity characteristic of the oil at the end of the interval. In short, if you used 15w40, are we still looking at 15w40 at the end?

 

[Pkruse]

If the lab report shows any problem with the oil, I change it. But that almost never happens. I take frequent samples with new equipment. After I understand the trend for that engine and that duty cycle, then I change oil and filter on a schedule suggested by that data, and I take samples less frequently.

 

[Pkruse]

The lab reports will tell .me the viscosity. Living in a hot climate, I only care about the "40" number. I don't pay for the "15W" number so I don't have that data. If I lived in a cold climate, then I'd pay attention to that data, too; and change the oil at first indication of a viscosity breakdown.

 

[Fahlin Racing]

The viscosity improvers will continue to do what they were designed for even after a long period of service if everything is kept clean then?

 

[Pkruse]

I don't pretend to understand the chemistry of the oil. I maintained a fleet of heavy equipment for 25 years, and I had an lubrication expert on staff for that. I changed the oil any time he said to. But more often he would say to change or filter the oil. In that case, I would pull the oil out, filter it, & put it back. That would also be an indication that I needed to increase the filter change frequency, or install a better filter. But I know of engines that were run for 50,000 hours with no oil change, torn down and inspected by factory engineers, and then reassembled and returned to service with all their original parts. This data was used to justify the elimination of the 50,000 hour overhaul required by the USCG for these marine engines. Those engines had much better filters than normal. Any time you change a filter, you also change about a quarter of the oil. This is sufficient to maintain the additive package.

 

[turbo]

I drive infrequently, but always drive at least 35-50 miles round-trip (mostly at least at 55 mph), so that the oil has plenty of time to heat up and drive off any water that has condensed in there. In light of that, I change my oil and filter when I feel like it, using my driving habits as a guide.

People driving short (but long-duration) commutes in stop-and-go traffic should adhere to the manufacturers' recommendations, but there are many of us who drive such as to allow gradual engine warm-ups and to allow any condensation to be driven off. If there is no water in your oil, there should be no acidification and no degradation of the oil additives.

 

[Pkruse]

Good advice to anyone not sending oil samples to a lab. Even better to send enough samples to a lab so as to understand how your engine trends with your duty cycle.

 

[Fahlin Racing]

Sure you wouldn't know everything chemically through fleet maintenance, but, it is a good tool in any type of equipment regardless of the usage which you are well aware of. I am just trying to pick your brain Pkruse, that's all. From what you have done mentioned in your posts obviously shows that if our oil is kept clean from all contaminants we encounter not only does the base oil stay in good condition but the V.I. do as well.

 

[Pkruse]

If you run an engine harder, then you have to change the oil or filter more often. For that reason, some OEM's offer an alternate to changing by miles. They offer maintenance by total fuel consumption. The Canadian coast guard idles their rescue boats all winter to keep them ready for a call. Their schedule might call for a filter change every 6000 gallons, for example. So if they get a lot of rescue calls, they would be changing it more often. If they install a better filter, then it is even less often.