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© 2003 Brian F. Schreurs
Even we have a disclaimer.
These are some of the interesting questions we've gotten about the synthetic oil life study. We can't honestly say they've been asked frequently, but they have come up, and we felt they merited a posted response.|
Some of these answers come from our own research, and some come by way of Blackstone Laboratories. Thanks to the Blackstone crew for helping out when we get stuck.
- What the heck is going on with the copper levels in the Mobil 1 test?!
- Good question. High copper is typical of the LS1 engine during its early life (pre-30k miles). As for where it comes from, that's still a bit of a mystery. We're studying the issue with the LS1 Engine Copper Levels page.
- Is the copper screwing up your test results?
- No. The copper level has no effect on any of the key factors in oil longevity. In fact, as long as the other particulates remain stable, the copper isn't having much of an effect on anything at all.
- The lab repeatedly asked whether you were using an additive that contains copper. How is it possible that additive copper is acceptable but wear copper is bad?
- Copper as part of an additive package is usually part of a fine molecular blend that is "smooth" at the particulate level. Copper as wear from a part of the engine is basically tiny metal shards that are highly abrasive. Still, our copper doesn't seem to be causing any real problems (all other particulates are pretty normal) so it's not something to get worked up about.
- How long do you let the car sit before you take your sample?
- Just the amount of time it takes to get a catch pan and a creeper under the car. The oil sample is so hot that on one occasion it melted our gloves to our hands. Ouch! Now we use high-temp gloves.
- Why is your fuel number out of whack at the Mobil 1 1,000 sample?
- This was the first sample we drew, and to be perfectly blunt we messed up. We let the car sit way too long and get too cool, and we took the first oil out of the tap instead of letting it dribble a bit first. We do not believe the fuel level in this sample is representative of the actual state of the oil, and the condition of the oil since then seems to bear this out. This is precisely why we're taking samples every 1,000 miles: to identify anomalies and discard them.
- How is it possible for the TBN to increase from the virgin sample to the 1,000 sample in the Mobil 1 test?
- Keep in mind that the virgin sample was from just one bottle while the first engine sample was with a mix from six bottles. It is entirely possible that the virgin sample was on the low side of the six-bottle average. Also, some observers have noted that TBN can actually go up during use, though this is quite rare.
- It would seem that the prime determinant of when the oil is expired is the TBN.
- Yep. The other properties seem to hold out well beyond the TBN's lifespan.
- But the oil analysis I have for my engine doesn't include TBN!
- Then you don't really know for sure whether your oil is expired.
- So if I manage to keep my TBN in good shape, how long before I have to change the filter?
- Watch your insolubles level. Once that gets beyond 0.6% it's time for a filter change.
- When are you changing YOUR filter? Didn't your website used to say every 5,000 miles?
- Yes, it did. But after discovering that our car consumes half a quart of oil every 1,000 miles, we decided that changing the filter would only add to the problem of refreshing the additive package in the oil. Instead, we'll change the filter when the insolubles level reaches or exceeds 0.6%. We made this change of procedure before the first filter interval, so all oil tests will still be equal in this regard.
- So you're using NAPA Gold filters? Any particular reason? And didn't your site used to say you're using Wix filters?
- Hey, that's three questions! We are using NAPA Gold filters. Our choice is one of convenience, though the test results we've seen show this filter to be decent for an off-the-shelf filter. We're not ashamed of it. The site used to say we were using Wix filters, but we changed it when we looked under the car and found out that we were actually using NAPA Gold filters. All oil has been and will be tested using this type of filter.
- Well, that's an embarrassing mistake. You probably feel pretty stupid.
- Hey, speaking of oil use, what's up with your car using half a quart of oil every 1,000 miles?
- It's annoying but pretty typical of today's cars. GM states that LS1 oil usage below 1 quart per 1,500 miles is normal.
- Is your Appalachian winter messing with the TBN in your test car?
- Not by a measureable amount, no.
- Hmmm, but I've done analyses in the past and they've shown a worse TBN in the winter.
- This can be caused by a couple of factors. First, in the winter many people allow their car to warm up before driving it. This right here uses oil life without it showing up in the mileage -- do it often enough and it adds up. Second, all that idling time causes fuel wash in the cylinders, contaminating the oil and using up the TBN faster. Third, traffic tends to stack up more in metro areas whenever the weather gets bad, adding to that idle time. None of these items are a factor here: we don't let the car idle in the morning and we don't get that kind of traffic in this area.
- Look, if we see a trend significantly penalizing oil tested in the winter, we'll run a re-test.
- Is Mobil 1 at a disadvantage because you started sampling when your engine had only 10,000 miles on it?
- Doubtful, but just to be sure we plan on re-sampling Mobil 1 after the first four oils go through the cycle. This will illustrate how repeatable the results of this test are.
- I'm a glutton for punishment, and I need some reading material. Got any recommendations?
- Sure. Here's the project's biblography to date:
- Amann, Richard W. et. al. 1997 GM 5.7 Liter LS1 V8 Engine. SAE International Technical Paper #970915, 1997.
- Basu, Amiyo et. al. "Smart sensing" of Oil Degradation and Oil Level Measurements in Gasoline Engines. SAE International Technical Paper #2000-01-1366, 2000.
- Bui, Katherine. "A Defining Moment for Synthetics, Part 1". Lubricants World, October 1999.
- Bui, Katherine. "A Defining Moment for Synthetics, Part 2". Lubricants World, November 1999.
- Clark, Jim. "pH (Titration) Curves". Chemguide website, 2002.
- CTC Analytical Services. "Oil Analysis Troubleshooting Guide". CTC Analytical Services Inc., undated.
- Delphi Corporation. "Intellek Oil Condition Sensor". Delphi Corp. product data sheet, 2002.
- "GM Oil Life System -- How Does It Know?". GM Tech Link, March 2000.
- Hertz, P. Barry. Summer '95 Engine Wear Investigations Using Canola Methyl Ester and No. 2 Diesel Fuels. Canodev Research Inc., 1996.
- Hertz, P. Barry. Winter Engine Wear Comparisons With a Canola Bio-Diesel Fuel Blend. Saskatchewan Canola Development Commission, 1995.
- Inoue, Kiyoshi, and Yousuke Yamanaka. Change in Performance of Engine Oils with Degradation. SAE International Technical Paper #902122, 1990.
- Kaleli, Hakan, and Behrooz Khorramian. Used Oil Analysis and Study of Oil Drain Period in Gasoline Engine. SAE International Technical Paper #981448, 1998.
- Macian, V., et. al. Oil Analysis Evaluation for an Engines Fault Diagnosis System. SAE International Technical Paper #1999-01-1515, 1999.
- Mayer, Ashley. "Oil Analysis, Part 1". AutoSpeed, Issue 126, 17 April 2001.
- Mayer, Ashley. "Oil Analysis, Part 2". AutoSpeed, Issue 127, 24 April 2001.
- McFall, David. "Drain Intervals: How Long Must We Wait?" Lubes & Greases, March 2003.
- National Tribology Services. "Application Note - Important Tests In Oil Analysis". National Tribology Services website, undated.
- OilAnalysis.com Learning Center. "GM's Oil-Life System Improves Timing of Oil Change". Noria Corporation website, undated.
- OilGuard Bypass Filters. "Understanding Oil Analysis". OilGuard Bypass Filters website, 2003.
- Pecuniary, Inc. "Oil Analysis". Pecuniary, Inc. website, undated.
- Schumacher, Leon G. Engine Oil Impact Literature Search and Summary. National Biodiesel Board, 1996.
- Standard Practice for Conversion of Kinematic Viscosity to Saybolt Universal Viscosity or to Saybolt Furol Viscosity. ASTM International Standard #D-2161-93, 1993.
- Standard Test Method for Acid Number of Petroleum Products by Potentiometric Titration. ASTM International Standard #D-664-95, 1995.
- Standard Test Method for Base Number Determination by Potentiometric Titration. ASTM International Standard #D-4739-96, 1997.
- Standard Test Method for Base Number of Petroleum Products by Potentiometric Perchloric Acid Titration. ASTM International Standard #D-2896-98.
- Standard Test Methods for Detecting Glycol-Base Antifreeze in Used Lubricating Oils. ASTM International Standard #D-2982-98, 1999.
- Standard Test Method for Determination of Additive Elements, Wear Metals, and Contaminants in Used Lubricating Oils and Determination of Selected Elements in Base Oils by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). ASTM International Standard #D-5185-97, 1997.
- Standard Test Method for Determination of Water in Liquid Petroleum Products by Karl Fischer Reagent. ASTM International Standard #D-1744-92, 1992.
- Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (the Calculation of Dynamic Viscosity). ASTM International Standard #D-445-97, 1998.
- Standard Test Method for Semi-Quantitative Field Test Method for Base Number in New and Used Lubricants by Color-Indicator Titration. ASTM International Standard #D-5984-97, 1997.
- Standard Test Method for Water and Sediment in Crude Oil by Centrifuge Method (Field Procedure). ASTM International Standard #D-96-88.