sampling

Sampling Methods

It’s a perfect spring day. There you are, merrily going about your business of changing the oil. But wait! You forgot the oil sample bottle! A quick scramble to retrieve the bottle gets you back to the oil just as the last of it drains out.

Can you pour a sample out of the filter instead? What if you add a quart a few days before sampling – how does that affect the analysis? What about something like an engine flush – should you use one? Do they work? Your investigative team at Blackstone experimented, and we’ve got answers. While these tests probably won’t qualify for a peer-reviewed journal, they’re a good guide to what you need to know about sampling.

This is part two in our series on sampling methods. Part one, on engine flushes and their effects on analysis, can be found here. Part two covers common sampling scenarios: does it change the results if you take a sample from the filter or dipstick? What if you add fresh oil before sampling? Is it a problem if the oil gets dark right after putting it in the engine? That last question isn’t about sampling methods, but people ask all the time and your investigative team at Blackstone wanted to know, so read on for answers.

Does it matter how you sample?

Our instructions for sampling say to catch a sample as the oil drains from the pan, but that doesn’t always happen. Does it change the date if you take a sample from the filter or pull it through the dipstick?

In short: no. Figures 1 and 2 illustrate three consecutive samples taken from two different cars: Figure 1 is from a Toyota Corolla and Figure 2, a Mercury Milan. The column on the left is a sample taken through the dipstick. The middle column was oil taken while the oil drained from the pan. And the right-hand column is oil taken from the filter.

Results

The samples are unremarkable in that there’s less than 1 ppm difference in the wear metals across all three samples. The sampling method seems to have no impact on the metals that show up in analysis.

The Corolla in Figure 1 does show a higher silicon reading in the sample taken from the oil filter, but perhaps that was due to either dirt collected by the filter that ended up back in suspension in the engine oil, or sample contamination – we did have to use a bit of creativity in removing that filter from the engine, as the filter was overtightened and stuck. (If you’re wondering, we stabbed it with a screwdriver to give us more twisting leverage – we did not sterilize the screwdriver before surgery, so it’s entirely possible some silicon was introduced in that process.)

Does adding fresh oil impact the test results?

It makes sense that that adding fresh oil will dilute the wear numbers. But how much do the numbers change? And does it matter when you add the new oil? In theory, if you have a 4-quart sump, adding one quart of fresh oil shortly before the oil change would mean that your engine’s metals are diluted by 25% from their previous numbers.

To test this theory, Ryan Stark, Blackstone’s president, pulled a sample from his MINI, then added a quart and sampled again to see how the numbers changed.

Crunching numbers

The MINI has a total capacity of 4.5 quarts, so the one quart he added comprised 22% of the total engine oil capacity. Most of the metals decreased by approximately the same percentage: iron dropped from 26 ppm to 20 ppm (a decrease of 23%), copper dropped by 25%, from 8 to 6 ppm. If we assume that chrome actually changed by less than 1 full ppm, due to rounding, the average change in metal works out to around 25%, which is what we’d expect from adding a quart of oil to this engine.

The only other appreciable wear metal in his sample is aluminum, which, interestingly enough, read at 5 ppm in both samples, showing no change at all. We couldn’t let that element go without a little suspicion – why didn’t it change when the other metals did? As it turns out, the actual number our spectrometer reads goes four decimal places to the right. We round to the nearest whole number on the report, but if we pull the full spectral data from those tests, aluminum read at 5.4290, and in the second test aluminum read at 4.8995. Both readings were rounded to 5 ppm in the report, but the full spectral data shows a slight change between the two samples, an improvement of 9.7%. So aluminum did change with the added oil, just not quite as much as the other metals and not enough to show on one of our published reports.

The “when” factor

There are other variables to consider like how far into your oil change you add the oil, and how much oil you add. If a quart of oil is added at the 3,000-mile mark and you run your oil 10,000 total miles, the dilution factor probably is going to be a lot different than adding a quart just before changing the oil. That’s harder to test for because there are too many variables to isolate.

So this isn’t the be-all-end-all of the dilution question, but it at least gives some insight into the fact that the metals could be diluted if you’re adding oil, especially if you’re doing it right before an oil change. It is a good idea to add fresh oil when low, even if you’ll be changing the oil soon. Running an engine on a diminished oil capacity isn’t great.

Why does my used oil look so dark?

We get a lot of questions from people who do an oil change then notice that their oil is dark immediately afterward. Is it a problem?

To get to the bottom of this question, we conducted two oil changes on two separate vehicles, idled the fresh oil for five minutes, then sampled and examined the new oil.

FIG 4: Toyota Corolla – Left, new oil. Middle, oil after 5 minutes. Right, used oil.

FIG 5: Mercury Milan – Left, new oil. Middle, oil after 5 minutes. Right, used oil.

In both cases, the oils were quite dark after just five minutes of use. In Figures 4 and 5, the virgin oil is pretty obvious, but there’s not much difference between the new oil with 5 minutes on it and the oil with several thousand miles on it. In terms of the overall sample color, it’s quite hard to tell.

Results

So does the dark oil indicate anything? Figures 6 and 7 show the analytical results of the new (but darkened) oil after being run 5 minutes in two different engines.

Both oils look very clean in testing, with minimal insolubles, no contamination, and very low metal counts. You might note that the metals do not start at 0 ppm – that’s because you never get 100% of the old oil out when you do an oil change. There’s always some carryover from one oil change to the next, and you can see that in the results.

So is it a problem that the oil looks dark right after an oil change? Nope. It’s fairly normal for oil to darken quickly after an oil change. If anything, it seems to suggest that the oil is doing just what it’s supposed to be doing: collecting contaminants and combustion by-products and keeping them in suspension so they can be removed when the oil is changed.

Sampling Methods: Go for it!

In the end, although we give you guidelines about how to sample, your method really doesn’t make too much difference. If you don’t catch a sample mid-stream, just let us know when you send the oil in and we’ll take that into account when we do the analysis. If anything unusual shows up and we think it might be related to something you did, we’ll let you know in the comments.

By Amanda Callahan|2024-09-19T09:14:05-04:002023|Articles, Gas/Diesel Engine|Comments Off

How Often Should I Sample?

One of the most common questions we get asked is, “How often should I send in a sample?” and this is one that I tend to struggle with answering.

The businessman in me says at every oil change regardless, and while you’re at it, check your transmission fluid, differential fluid, and your wife’s/husband’s car. And don’t forget any air compressors, lawn mowers, wood splitters, etc. you may own. And your neighbor’s car was smoking a bit last time you saw it drive past, better check that too.

Unfortunately, before I start talking, my “realist” side kicks in and I usually say something like once a year, after you have some good trends established. But even that answer doesn’t always apply. What if you don’t drive your vehicle very often, or at all? Is it really necessary to test the oil once a year? The answer to that is once again not really. Though if you think you might have a problem developing, then it could be a good idea to sample more often than you normally would.

Old oil

We recently had a customer send in a sample of oil that was in an engine for 10 years and had not been run at all in more than 5 years — and amazingly enough wear metals were virtually identical to what we were seeing when he last sampled 10 years ago.

The only significant difference was at insolubles. These had gone from 0.2% to 0.0% after the 5 years of sitting. We figured the reason for this was gravity. All normal engine oils contain dispersant additives, and their function is to hold dirt and solids in suspension so they can be filtered out. Do they work? Absolutely, but asking them to work for a full five years is a little much. The good news is that the additives are still in the oil, so once the engine starts up and sees some use, those solids should be picked up and dispersed again.

So, if we can say with good certainty that the oil itself won’t go bad just sitting in an engine, you might wonder why it needs to be changed at all? The answer to that is contamination.

Contamination problems

Engine oil has maybe the hardest life of any oil application out there. Not only does it see frequent temperature swings of 150° to 200°F (65° to 90°C), but it will also get contaminated with fuel blow-by and a little atmospheric water as well.

Ideally the fuel and water will boil out once the oil gets up to operating temperature, but that contamination will add up over time and eventually cause the oil to start to oxidize. If you can pinpoint exactly when the oil will oxidize enough that it will start to affect wear or cause the oil’s viscosity to change, that’s the point at which you want to change the oil. If you test your oil on a regular basis, you can start to identify that point and that’s one of the reasons why we’re here.

So when is the best time to get a sample? The answer to that is: it depends.

Best time to sample?

If you just bought a brand-new car, the first oil is factory oil and while that oil will sometimes have an unusual additive package, it’s not that useful for finding a problem, or developing a normal wear trend.

Factory oil is typically loaded with excess metal from wear-in of new parts as well and some silicon from sealers used when the engine was assembled, and this stuff normally takes two or three oil changes to wash out.

So, while these samples aren’t useful as far as trends go, they are useful in finding problems in engines that have been recently rebuilt or had other major work done, and we always recommend testing those from the beginning. This is because if wear metals don’t drop from that initial oil fill, it can be the early indication of a problem.

It’s always a good idea to get a trend going while the engine is running well. A trend consists of three samples. Once we have that established and the engine is running perfectly, then it’s not really necessary to get a sample at each oil change and at that point it’s okay in most cases to go to a once-a-year sampling routine.

Once a year?

You might be wondering why once a year? The reason for that is two-fold. One: A lot of people (including myself) only change their oil once a year. It’s also the only time I crawl under my car and have the hood open. I consider it like an annual inspection and there are been numerous times that I have been on my back waiting for the oil to drain when I noticed another problem like a seeping freeze-plug or a torn CV boot. Two: It’s easy to remember.

However, the once-a-year rule doesn’t always apply. There are many vehicles out there that only see light use (maybe less than 500 miles a year), so not only can they typically skip changing oil on a yearly basis, then don’t need to sample every year.

Another factor is how important the vehicle is to you. If you rely on it for your business, or it’s the only vehicle you have and it’s getting up there in mileage, then sampling at every oil change might be a very good idea.

Engines speak before they fail

We can see problems developing in your engine long before they actually cause a failure, so you normally have some time to do something about any trouble we might spot. Still, like a lot of things in life, the earlier you know about problems the better.

We get as lot of samples from engines that have a known problem, so we test the oil and usually see poor wear, but telling how bad the problem is or how/when it started is hard without trends from when the engine was normal. We do have averages that give us a good idea how an engine should look overall, but they aren’t as valuable as trends when it comes to saying exactly what’s normal for a particular engine and the use it sees.

So there you have it, I’m actually saying you may not need our services as much as you might think. Some of the other business owners out there might call me crazy and I guess they’re right. But please, feel free to sample anytime you like. As you know there is nothing better than getting a glowing oil report on your pride and joy.

By Ryan Stark|2024-09-19T09:34:43-04:002023|Articles, Gas/Diesel Engine, Marine|Comments Off

Annual Inspection

Well, the building is over and my RV-12 is in the air. Now that I’ve got an airplane I can actually use to go places and have fun, life is a bit less hectic. Still, the fun has to stop sometime and for airplane owners, the opposite of fun is often the annual inspection. Since my aircraft is an experimental, I have to do what’s known as a condition inspection. There is maybe less paperwork involved than the annual inspection that certified aircraft have to go through, but the potential for pain is there. To be clear, this inspection is an extremely important thing to do and the pain will often be limited to just a lack of flying, though there is always the possibility that a major repair will be needed and then the pain can quickly spread to your wallet.

Inspection #2

I am actually on my second condition inspection. The first one was done in July of 2021 and it went really well. The airplane was new (only 26 hours on it), so there really weren’t any issues involving worn-out parts and other things that older aircraft have to deal with. Nope, just checking to make sure everything was working properly and all the fasteners were still holding fast.

This year has been different, but it’s not really the plane’s fault. My wife and I started the inspection in mid-July, when the weather was nice and there was still plenty of year left, but didn’t get it completely done until just last weekend (the end of January). Again, the plane is still fairly new (only at 46 hours now), so there really weren’t that many problems to address. No, this year the problem was with me. Life and work tend to have a way of keeping you busy and this year it’s been a struggle to string a few weeks together to do the inspection.

DIY maintenance

As many of you with experimental aircraft know, one of the perks of building an airplane is getting to do all of your own maintenance. No more having to find a mechanic and work around their schedule or pay their bills. The other side of the coin is, you have to do all your own maintenance. In fact, there isn’t a mechanic in this area that will touch an experimental aircraft, so I couldn’t hire this job out even if I wanted to. Thankfully, the work itself is pretty simple overall and the nice thing is there is a checklist to follow. These are printed in the maintenance manual and include a systematic checklist of everything that needs to be looked at.

I don’t think you have to be especially mechanically inclined or talented to do this job yourself, but a little mechanical knowledge probably helps. I took a 2-day class in Dallas to get a repairman certificate with an inspection rating. It was full of good information, but possibly the most important thing they did was show all the many ways people can die as a result of taking shortcuts and not following the checklist. By the time I was done with that class, I was fairly gripping the chair arms with white-knuckled fists, and ready to triple check to make sure I dotted all my i’s and crossed all my t’s.

Oil change at annual

The checklist has all kinds of things on it, and I can see how it might be tempting to skip something that seems unnecessary. One of the things on that checklist is normally an oil change. This is a standard part of most annuals and often times it’s done whether the oil actually needs changed or not. We see short-run samples like this all the time at Blackstone and often wonder if the owner is looking for a problem, or if the plane is just in for annual and this was on the list.

In my mind, if there was any one item on the inspection checklist that could be skipped, it would be an oil change that’s not needed (Blackstone’s lawyers would like to remind you that this is one man’s opinion only; officially, Blackstone advises you to follow the checklist!). Still, with that being said, an oil change is really an excellent diagnostic tool. You can send in an oil sample to see if the engine is wearing poorly and cut open the oil filter to see if it has any visual metal present. The problem with a short-run sample is, we can rarely tell the customers a lot other than there wasn’t much metal in the oil, so it looks okay from what we can see.

Unless you suspect a problem, a short-run filter inspection would also be of minimal value, for the same reason—there really isn’t enough time for any significant metal to accumulate. So how about a situation where you are halfway through a typical oil change? Where you have enough time on the oil for an analysis to tell you something, but not enough time that the oil really needs to be changed? For situations like that, you might want to get an oil sample by pulling one up via the dipstick tube. We sell a pump for just that purpose. It’s reusable and the money you’d save on an unnecessary oil change would likely pay for the pump in pretty short order.

Sampling from the filter

Or, what might be an even better option is to just change the oil filter at that point. Then you can pour an oil sample right from the filter and still cut it open to look for metal. If you do follow this route, just let us know you got the oil sample from the filter. We might see a little more insoluble (solid) material in this situation, but the metals and all other results should be basically the same as if you got the oil as it was draining out of the sump.

We understand there might be some situations where it’s not possible to stray from the checklist and it’s just easier to dump the oil and start fresh, though if you have some leeway in that regard, skipping an oil change can save some time and money, making a potentially painful job a little less so.

By Ryan Stark|2024-09-18T14:20:13-04:002023|Aircraft, Articles|Comments Off

Pre-Buy Samples: The Art of the (Craigslist) Deal

Taking a sample before buying a new plane or boat is common practice in the aviation and marine industries, and it’s just as useful for anyone looking for their next car, truck, or motorcycle. If you’re anything like us, you probably spend an unhealthy amount of time browsing the local classifieds and Craigslist hunting for the elusive bargain. And although oil analysis can’t stop you from making a wire transfer to your new foreign royalty business associate, it can help you avoid buying a total lemon, and maybe even calm your nerves on the initial drive home.

Pulling a sample before plunking down the dough is a good move. We’ll test the oil for excessive amounts of metal, contamination, and solids. We compare your results to our database of samples from similar makes/models, giving you a good look at how internal parts are getting along, and if there are any looming problems driving the current owner to sell you their beloved ride. We’re familiar with common problems for certain engine models and years, and we know how different issues look in analysis.

It can be tricky to gauge whether excess metals are from poor wear or from how the engine has been used, especially if you don’t know how long the oil has been run. But even if the oil was recently changed, we can still often see evidence of serious problems. Maybe coolant has just started getting into the oil, but there’s not yet enough to give the oil that telltale milkshake appearance. It takes a pretty bad internal coolant leak to cause a visual change to the oil, but it doesn’t take much coolant to show up in analysis.

You’ll also learn the oil’s viscosity range, which can show if the current owner was using the correct grade. Analysis will also pick up on things like dirt from an intake leak or excess fuel from an injector issue. We always point out any potential problems in the report comments, and try to provide possible reasons for abnormal findings in the comments to help you make sense of the results.

Most private owners and dealerships will allow you to collect a sample, at least with a bit of persuasion. The current owner has a vested interest in the health of their vehicle, and offering a copy of a report might help even if you don’t go through with the purchase.

We sell a vacuum https://www.blackstone-labs.com/products/vacuum-pump/pump so you can take a sample through the dipstick right then and there, while you’re looking at the vehicle. Samples can also be taken by loosening the oil filter or drain plug enough for some oil to drain out — just be sure to clean the area around the sample collection point if you go this route. If a seller refuses to let you collect a sample without good reason, that alone might be the red flag that sends you running.

Getting results in a hurry

We know you’re working on a tight schedule to make the deal happen, so if you don’t have a kit on hand when you go to look at your new ride, don’t fret. You can send the oil in any clean, plastic container with a screw-on lid. Just be sure to collect enough oil for testing (about 100 mL or 3 ounces, which is a little less than half a cup), and package the sample appropriately so it doesn’t leak in transit. The same information slips included in the kits can be found on our website. We appreciate all the info we can get about a sample, as it helps make sense of the results so we can provide the best possible report in return.

Buying a used vehicle can be an adventure, and we’re here to help you make the most informed decision possible!

By Ryan Stark|2024-09-19T10:17:51-04:002023|Articles, Gas/Diesel Engine, Marine|Comments Off