Oil Analysis
AMSOIL Oil Analysis — Extend Drain Intervals & Catch Engine Wear Early
Oil analysis is a laboratory test of a used oil sample that measures wear metals, contamination, viscosity, and additive depletion. It tells you the actual condition of the oil and engine — not just calendar miles. Used routinely, oil analysis lets fleets and operators safely extend drain intervals, catch internal wear early, and prevent failures before they become catastrophic.
Why Run Used Oil Analysis?
- Verify safe extended drain intervals on AMSOIL synthetic oil
- Catch internal wear (bearings, rings, cylinders) months before failure
- Detect fuel dilution, coolant intrusion, and water contamination early
- Track trends across multiple samples on the same sump
- Used by commercial fleets, mining, military & over-the-road truckers
- ISO 17025-accredited lab — Oil Analyzers Inc.
- Digital reports typically returned within a few business days
- Pays for itself the first time it catches a developing problem
What Oil Analysis Measures
What Does Oil Analysis Tell You About Your Engine?
A complete used oil analysis report covers six categories. Each category, in isolation, is a snapshot — but tracked across multiple samples on the same sump, the trends become a powerful early-warning system:
| Category | What's Measured | What It Indicates |
|---|---|---|
| Wear Metals | Iron, copper, lead, aluminum, chromium, tin | Internal component wear — bearings, rings, cylinders, bushings, pistons |
| Contamination | Water, fuel dilution, coolant (glycol), silicon (dirt), soot | Air-filter or seal failure, head-gasket issues, injector or fuel-system problems |
| Viscosity | kV @ 100°C vs. spec grade | Fuel dilution thinning the oil, oxidation thickening it, wrong grade added |
| Oxidation & Nitration | FTIR oxidation & nitration values | Oil age, heat exposure, blowby, end of useful oil life |
| Additive Depletion | Calcium, zinc, phosphorus, magnesium, boron | How much detergent/anti-wear additive is left in the oil |
| TBN / TAN | Total Base Number / Total Acid Number | Acid-neutralizing capacity remaining (TBN) vs. acid buildup (TAN) |
Step-by-Step Guide
How to Submit an Oil Sample for Analysis
Drawing a clean, representative sample is critical to accurate results. Follow these six steps for engine, transmission, hydraulic, gear, or compressor sumps:
- 1
Order an Oil Analyzers Inc. test kit
Order an AMSOIL / Oil Analyzers Inc. used oil analysis test kit. Each kit includes a sample bottle, vacuum sample pump (if needed), unit-information label, and a prepaid return mailer. Multi-packs are available for fleets and operations sampling multiple sumps.
- 2
Run the engine to operating temperature
Drive or run the engine until the oil reaches normal operating temperature — this ensures wear metals, fuel, water, and contamination are evenly suspended in the oil rather than settled at the bottom of the sump. A cold sample can give misleading low readings.
- 3
Draw a 2–4 oz sample
Use the included vacuum sample pump and tubing through the dipstick tube to draw 2–4 oz of oil into the sample bottle, OR capture a mid-stream sample during a hot drain (avoid the very first or last oil out of the pan, where contamination concentrates). Seal the bottle immediately.
- 4
Fill out the unit-information label
Complete the unit-information label or online form: equipment make/model, engine hours or vehicle miles, oil brand and grade, hours/miles on the oil, and any makeup oil added. Accurate information is essential — the lab uses it to interpret your wear metal and contamination numbers.
- 5
Mail the sample in the prepaid container
Place the sealed sample bottle in the leak-proof container, drop it in the prepaid mailer, and put it in the mail or your shipping out-tray. The lab typically receives, processes, and reports results within a few business days of receipt.
- 6
Review your report and act on it
You'll receive a digital report with wear metals, contamination, viscosity, oxidation, nitration, and TBN/TAN values, plus a written condition rating and recommendation — change now, change at the normal interval, or extend the drain. Save reports to track trends across multiple samples on the same sump.
Reading Your Report
How to Read Your Oil Analysis Results
Your Oil Analyzers Inc. report comes back with a condition rating and a written recommendation. Here's how to interpret the numbers behind it:
1. Look at the condition rating first
Most reports use a Normal / Marginal / Critical (or similar) rating with a written recommendation. If it says "extend the drain," your oil and engine are healthy. If it says "change the oil now" or "investigate further," read the wear-metal and contamination sections carefully before running the engine again.
2. Check wear metals against the trend, not the absolute value
A single iron reading of 30 ppm means very little. The same engine going from 12 ppm to 30 ppm to 60 ppm across three samples is screaming about a developing problem. Trend wear metals across at least three samples on the same sump before drawing conclusions.
3. Watch contamination — coolant, fuel, water, silicon
Coolant (glycol) in the oil is a head-gasket or oil-cooler red flag. Fuel dilution above 3–5% indicates injector or combustion problems and accelerates wear. Silicon trending up means dirt is bypassing the air filter. Water above ~0.2% indicates condensation or coolant leaks. Any of these warrant immediate investigation.
4. Confirm viscosity is still in-grade
A 5W-40 should still be in the 12.5–16.3 cSt @ 100°C range. Viscosity dropping below grade usually means fuel dilution; rising above grade usually means oxidation or soot loading. Out-of-grade oil should be changed regardless of other readings.
5. Check oxidation, nitration, and TBN for remaining oil life
FTIR oxidation and nitration values rising sharply mean the oil is at end of life. TBN (Total Base Number) dropping below ~50% of new-oil baseline means the oil's acid-neutralizing capacity is depleted. Either condition means change the oil now, even if wear metals look fine.
Who Uses Oil Analysis?
Oil analysis is the standard maintenance tool for any operation where downtime is expensive and engine failure is unacceptable:
Commercial Fleets
Box trucks, vans, service vehicles, refuse trucks. Per-unit sampling supports extended drain intervals and predictive maintenance.
Over-the-Road Truckers
Class 8 diesels — Cummins X15, Detroit DD15, PACCAR MX-13, Volvo D13. Sample every drain to verify extended intervals safely.
Diesel Pickup Owners
6.7L Cummins, 6.7L Power Stroke, 6.6L Duramax. Sample to safely run AMSOIL synthetic on extended intervals.
Mining & Construction
Excavators, dozers, haul trucks, loaders. Caterpillar, Komatsu, Volvo CE — sampling is standard predictive maintenance.
Heavy Equipment Rental Fleets
Sample at every major service to detect customer abuse, contamination, and developing wear before equipment fails on rent.
Marine Operators
Inboard diesels, gensets, commercial fishing, charter boats. Catch fuel dilution and water intrusion before catastrophic failure.
Stationary Generators
Standby and prime power gensets. Sample annually or per service interval to catch developing wear in low-hour engines.
Military & Government Fleets
DoD and federal fleet maintenance programs use routine sampling as standard practice across tactical and support vehicles.
Agricultural Operations
Tractors, combines, irrigation engines. Sample before and after planting/harvest to verify equipment health for the next season.
The Complete Guide to Used Oil Analysis
Why oil analysis exists
Calendar-mile and calendar-hour drain intervals are conservative one-size-fits-all guidelines. They assume the worst-case duty cycle, the worst-case fuel quality, and the worst-case operator. Oil analysis replaces that assumption with measurement: this specific sump, in this specific engine, with this specific oil, has X amount of life remaining. That's how fleets, mining operations, and the military extend drain intervals safely while reducing failure risk at the same time.
Why AMSOIL synthetic + oil analysis is a powerful pairing
AMSOIL synthetic motor oils are engineered to support extended drain intervals — but the maximum safe interval depends on your specific engine and duty cycle. Pairing AMSOIL synthetic oil with routine oil analysis from Oil Analyzers Inc. gives you the data to extend confidently: shorter intervals when conditions are harsh, longer intervals when the data supports it. The result is fewer total oil changes, less waste oil, and better protection.
Wear metals — what each one means
Iron usually traces to cylinder liners, camshafts, valve train, or crankshafts. Copper most often traces to bearing wear or oil cooler corrosion. Lead is bearing overlay material — rising lead is a bearing-failure red flag. Aluminum traces to pistons, certain bearings, and thrust washers. Chromium points at piston rings or valve stems. Tin traces to bearings and bushings. The lab interprets these together — no single metal in isolation tells the whole story.
Contamination — the most actionable category
Contamination is where oil analysis pays for itself fastest. Coolant (glycol) detected in oil is a head-gasket, oil-cooler, or EGR-cooler failure in progress. Fuel dilution above 3–5% indicates a leaking injector, poor combustion, or excessive idling — and it accelerates wear by thinning the oil and washing down cylinder walls. Silicon (dirt) trending up means an air-filter or intake-tract leak. Catching any of these early prevents catastrophic engine damage.
Trends beat single samples
The single most important rule in oil analysis: trend the same sump across multiple samples. A baseline sample at the first AMSOIL change establishes "normal" for that engine. Subsequent samples are compared against that baseline and against industry data for the same engine family. A wear metal climbing steadily across three or four samples is far more meaningful than a single high reading on one report.
Oil Analysis — Frequently Asked Questions
What is oil analysis and how does it help extend engine life?▾
What is an oil analysis test?▾
How does AMSOIL oil analysis work?▾
What does oil analysis tell you about your engine?▾
Who should use oil analysis?▾
How much does oil analysis cost?▾
How do you submit an oil sample?▾
How often should I run oil analysis?▾
Order Your Oil Analysis Kit
A single test kit is the cheapest insurance policy you'll ever buy on a diesel engine. Fleet customers — ask about multi-pack pricing and account programs.