ISO 4113 calibration fluid is the light, petroleum-based oil that stands in for diesel on the test bench where a workshop checks injection pumps and injectors. ISO 4113 is the international standard that says what it has to be like. How easily it flows and how much a liter weighs are held between a minimum and a maximum very close together (the range), so that two benches measure the same part the same way.
What is ISO 4113 calibration fluid?
It is the liquid that runs through the test bench in place of diesel, so that the measurement of each part can be trusted. Think of a fuel pump at the filling station: when it reads 1 liter, it has to deliver 1 liter, and an inspector checks it against a standard measure. Diesel engine injection parts work the same way, only the dose is tiny.
The injection pump pressurizes the fuel and sends each cylinder its dose. The injector is the tip that sprays that dose into the cylinder, like a plant mister working at much higher pressure. If one injector delivers more than another, the engine shakes, puffs black smoke and burns more fuel.
That is why the part goes to the test bench, a machine that turns the pump the way the engine would and makes the injectors fire hundreds of times into graduated tubes, the test cylinders. In a pump test, those injectors are the bench's own calibration injectors. What comes out is the delivery: the volume the part supplies over a fixed number of injections. Calibrating means comparing the delivery with the part maker's table to approve, adjust or reject.
The fluid running through all of this is a mineral oil (made from petroleum), refined (cleaned of unwanted molecules) and without a strong smell. It is far lighter than the base oils used in most lubricants, and it flows almost like diesel itself.
In newer engines with a common-rail system, a high-pressure pump fills a shared tube (the rail) connected to all the injectors. The injector decides the dose, opened and closed by the electronic control unit. These benches also use calibration fluid, and many measure delivery with an electronic meter instead of a test cylinder.
Figure 1. The fluid leaves the reservoir, passes through the injection pump and reaches the injectors, which fill the test cylinders, where the delivery is read.
If the fluid takes diesel's place on the bench, a question remains: why not use diesel itself?
Why doesn't the test bench use diesel itself?
Because diesel changes from one batch to the next, and a measurement can only be trusted if the liquid does not change. Think of a rubber ruler that stretches a little with each use: the same table measures 1.20 m one day and 1.23 m the next.
Diesel is that ruler. Depending on the batch, the refinery and the region, it comes out a little thinner or thicker, and in Brazil it also carries a share of biodiesel (fuel made from vegetable oil or fat). When the liquid changes, the bench reading changes with it, even with an identical part.
Calibration fluid is the steel ruler: the reference standard, which leaves the factory in a narrow range and is checked every week on the bench. With the fluid within the standard and the bench holding it at a fixed temperature (the next section shows why), a delivery outside the table points to the part, the adjustment or the bench itself.
Safety matters too: the diesel specification allows it to give off flammable vapor at much lower heat than calibration fluid.
Why do viscosity and density define calibration?
Because the dose that reaches the test cylinder depends on how easily the fluid flows and, in some injectors, on how much it weighs. Honey flows slowly and water flows fast: that resistance to flow is called viscosity.
Inside the pump, the dose is pushed by a plunger that runs in a barrel, like the plunger of a syringe. Between the two there is a clearance of thousandths of a millimeter, and with each push (each stroke) a little fluid slips through, as in an old syringe.
Thinner fluid slips through the clearance more, so the test cylinder receives less; thicker fluid slips less, and it receives more. The same part gives different deliveries.
Viscosity drops when the fluid warms up, like hot cooking oil, which flows more easily. That is why the bench keeps the fluid at a controlled temperature and the standard fixes viscosity at a single temperature.
Density is how much a liter of the fluid weighs. In injectors that dose by how long they stay open, such as common-rail ones, the dose is what passes through the fine hole during that time. It is like pushing a loaded wheelbarrow with the same force: at the same pressure, the heavier fluid leaves the hole more slowly and, in the same time, a slightly smaller volume passes.
That is why ISO 4113 tightens both measurements, viscosity and density.
How this shows up in your workshop:
the same pump gives one delivery right after the bench is switched on, with the fluid still cold, and another in the afternoon, with it warm;
two benches disagree about the same part;
the technician changes the adjustment of a part that was fine.
Figure 2. On the same part, thinner fluid slips through the clearance more, and the test cylinder receives less (clearance and difference exaggerated in the drawing).
Figure 3. At the same pressure and for the same time, heavier fluid passes a slightly smaller volume through the injector hole (difference exaggerated in the drawing).
For those who need the number: the standard uses kinematic viscosity (measured by the time the fluid takes to flow through a fine tube), in mm²/s, the same as cSt. New fluid has a viscosity of 2.45 to 2.75 mm²/s at 40 °C and a density of 0.820 to 0.830 g/mL at 15 °C.
S10 diesel (with up to 10 mg/kg of sulfur) can range from 2.0 to 4.5 mm²/s at 40 °C under Resolution No. 968/2024 of the Brazilian National Agency of Petroleum (ANP). ISO 4008-3, the test standard for injection pumps, asks for the fluid at 40 ± 2 °C, measured at the point where the bench connects to the line feeding the pump.
What does the ISO 4113 standard require?
Beyond the measurement, the standard covers safety, evaporation, service life, color, cold, parts, reading and composition, each item with its own test. The figure shows the map. The terms in the labels (flash point, cloud point, aromatics) are explained in the list just below:
Figure 4. Each group of ISO 4113 requirements protects one part of the work on the bench.
The measurement: viscosity and density, as you have just seen.
Safety: the flash point is the lowest temperature at which the fluid's vapor ignites for an instant with a flame nearby (alcohol ignites easily; cold cooking oil does not).
Evaporation: distillation shows how much of the fluid evaporates up to each temperature. The standard limits the light part, which evaporates and disappears from the reservoir, and the heavy part, which would make the fluid too thick.
Service life: the fluid slowly reacts with oxygen in the air (oxidation, which turns cooking oil rancid when left open). The standard ages it on purpose and measures the sludge (a residue that settles out) and the acidity that form.
Color: the standard limits it, because dark fluid gives away incomplete refining, oxidation or dirt.
Cold: the cloud point is the temperature at which the fluid turns hazy, because its paraffin (the part that turns to wax) forms crystals, which can clog the bench filter.
Parts: tests for rust on steel and for corrosion on copper and its alloys, such as brass and bronze, plus a limit on water, which helps rust form.
Reading: foam, because a bubble takes up room in the test cylinder and misleads the volume.
Composition: a ceiling on the aromatic part, one of the types of molecule in petroleum. The standard sets it through CA, the percentage of carbon in aromatic rings (the abbreviations come before the table, just below; see also the article on paraffinic, naphthenic and aromatic oil).
There are also three general requirements:
Additives: the fluid may carry chemicals in small doses that reinforce a quality (against foam, aging, corrosion and wear).
Health: it cannot contain a component in an amount that does harm, such as irritating the skin.
Storage: a calibrated part stored without cleaning, with the fluid still inside, has to work after at least 1 year.
For those who need the number: the table summarizes Table 1 of ISO 4113:2010. ISO 4113 has four designations, the names that go on the label: the basic one, CV, AW and CV-AW (explained in the next section). The CV column gives the narrower-range version; the last row applies only to the AW (anti-wear) versions. To read the table, four abbreviations:
IP 306 is the method that ages the fluid on purpose: 48 h heated, with oxygen bubbling through and a copper catalyst;
acidity in mg KOH/g tells how many milligrams of a base, potassium hydroxide, neutralize the acidity of 1 g of fluid;
CA is the percentage of carbon atoms that sit in aromatic rings, six-carbon rings like the one in benzene, unlike naphthenic rings, which are also closed but saturated;
"sequence I" is the first stage of the foam test, at 24 °C. In it, tendency is the volume of foam right after 5 min of blowing air into the fluid, and stability is what remains after 10 min of rest.
| Property (unit) | ISO 4113 (basic) | ISO 4113-CV | Method |
|---|---|---|---|
| Kinematic viscosity at 40 °C (mm²/s) | 2.45 to 2.75 | 2.50 to 2.55 | ISO 3104 |
| Density at 15 °C (g/mL) | 0.820 to 0.830 | 0.8235 to 0.8265 | ISO 3675 |
| Flash point, closed cup, that is, with the lid on (°C) | minimum 75 | minimum 75 | ISO 2719 |
| Distillation (% by volume) | at most 5% up to 210 °C; at least 95% up to 360 °C | same as basic | ISO 3405 |
| Accelerated aging with catalyst, 48 h | sludge up to 0.05% by mass; total acidity, measured after aging, up to 0.7 mg KOH/g | same as basic | IP 306 |
| Cloud point (°C) | maximum -10 | same as basic | ISO 3015 |
| Rust, in two tests | steel panels: 5 of 6 faces passing on 3 panels, 50 h in a humidity chamber; steel immersed in the fluid with water: pass | same as basic | ASTM D1748 and ASTM D665 (procedure A) |
| Copper strip corrosion, 3 h at 100 °C (class 1, slight tarnish, to 4, corrosion) | class 1 | same as basic | ISO 2160 |
| Water content (mg/kg) | maximum 500 | same as basic | ISO 12937 |
| Aromatic carbon, CA (%) | maximum 12 | same as basic | ASTM D2140 |
| Foam, sequence I, at 24 °C (mL) | tendency up to 50; stability 0 | same as basic | ASTM D892 |
| Color (ASTM scale, from 0.5, nearly colorless, to 8.0, dark) | maximum 2.0 | same as basic | ISO 2049 |
| Wear, AW versions only: scar diameter (mm) | maximum 0.8 (only in ISO 4113-AW) | maximum 0.8 (only in ISO 4113-CV-AW) | ASTM D2783, modified by ISO 4113 |
What do CV and AW mean in ISO 4113?
They are the two extra requirements the standard offers on top of the basic fluid: CV tightens the measurement, and AW protects the new part. Hence the four designations: ISO 4113 (the basic one), ISO 4113-CV, ISO 4113-AW and ISO 4113-CV-AW (both, in that order).
CV stands for closer value, a narrower range. An ordinary ruler and a caliper measure the same part, but the caliper errs less. CV fluid has viscosity and density tightened even further, for more accuracy in adjustment, such as when comparing benches.
Figure 5. Viscosity at 40 °C: S10 diesel can range from 2.0 to 4.5 mm²/s; ISO 4113 accepts 2.45 to 2.75, and ISO 4113-CV, 2.50 to 2.55.
AW stands for anti-wear. A machined surface looks smooth, but up close it is full of peaks, like very fine sandpaper. When a new or reconditioned part first runs, the break-in, the peaks of the plunger and the barrel press together under the initial load. They can weld to each other (the term the standard itself uses for this defect) and tear out material.
AW fluid carries an additive that forms a thin chemical layer on the surfaces and prevents this sticking. It helps the break-in on the bench; afterwards, in the engine, it is the diesel itself that lubricates the pump.
Figure 6. During break-in, the chemical layer of the anti-wear additive protects the peaks of the new surfaces.
For those who need the number: AW is checked in the four-ball test (ASTM D2783, an extreme-pressure test, which ISO 4113 itself modifies). In it, a steel ball spins pressed against three stationary ones, in the fluid, in three runs of 10 s at 1,450 rpm and 500 N; no wear mark on the balls may exceed 0.8 mm.
How do you know whether the bench fluid is still good?
By measuring viscosity every week and replacing all the fluid in the reservoir (the charge) when it passes the discard limit, the value at which the fluid leaves service: 3.0 mm²/s at 40 °C. The most widely used criterion comes from ISO 4008-3, the standard for testing injection pumps, which ISO 4113 itself cites in a note to its table.
With use, the fluid changes for five reasons:
the light part evaporates;
traces of lubricating oil and diesel get in;
moisture from the air condenses;
wear particles arrive;
air and heat oxidize the fluid.
ISO 4008-3 sets only one discard limit, the upper one, and links the rise in viscosity to three causes: the light part that evaporates, and traces of lubricating oil and of fuel. Evaporation and lubricating oil always thicken the fluid.
Diesel has a much wider range than the fluid and, depending on the batch, can thicken or thin it; that is why it is worth also tracking how far the charge has moved from the range of the new fluid.
Water and particles barely change viscosity, but they rust and scratch the parts, and oxidation darkens the fluid and makes it acidic. That is why color, acidity, water and particles complete the picture.
ISO 4008-3 also forbids correcting viscosity by mixing in another liquid (clause 6.4.2.6): once past the limit, the charge is replaced.
In the workshop, the signs are usually a delivery that changes on the same part on different days, dark or hazy fluid in the reservoir and the bench filter clogging sooner than normal.
The same standard gives storage precautions:
original sealed packaging, stored under cover, with the manufacturer's name and the standard number;
no condensed water in the reservoir or in stock;
fluid that has gone below -10 °C, the maximum cloud point ISO 4113 accepts, may have formed paraffin crystals and returns to use only on the manufacturer's guidance.
ISO 4008-3 dates from 1987, before common-rail. So on a common-rail bench, the procedure of the bench maker and the part maker has the final word, including on the limit and the replacement interval. On the others, the standard's limit applies and, with it, the replacement interval the bench maker indicates.
Figure 7. Illustrative example: viscosity rises week after week; once it passes the ISO 4008-3 limit, the charge is replaced.
For those who need the number: the discard limit is 3.0 mm²/s at 40 °C (ISO 4008-3, clause 6.4.2.4). The range for new fluid applies only to it; fluid in use is judged by the limit.
Which ISO 4113 calibration fluid should you use on the bench?
The one for the designation the test procedure asks for (the script written by the maker of the bench, the pump or the injector, or by the test standard). When in doubt, ISO 4113-CV-AW covers all four designations at once, because it meets the basic one, the narrow range and the anti-wear requirement.
| If on your bench… | Use | Why |
|---|---|---|
| Pump or injector test by a procedure that cites only ISO 4113 | ISO 4113 fluid (basic) | Meets the viscosity and density range and the standard's other requirements |
| Fine adjustment, comparison between benches or laboratory | CV designation | The narrower range gives more accuracy in adjustment |
| New or reconditioned part, on first run | AW designation | The anti-wear additive helps the break-in |
| Conventional and common-rail pumps and injectors, with a single fluid | Keen Fluid FC 4113 (ISO 4113-CV-AW) | Combines the narrow range and anti-wear protection |
What does Keen Fluid FC 4113 deliver?
Kelpen Oil formulates Keen Fluid FC 4113, an injection pump test fluid made from low-viscosity mineral oils. It meets ISO 4113-CV-AW (tight range and anti-wear) and is indicated for calibrating injection pumps and injectors, conventional and common-rail. It delivers standardized adjustment of injection pumps and injectors, that is, a calibration that repeats the same from one bench to another, because the fluid follows the standard's range, and protection against oxidation, which darkens the fluid and makes it acidic.
It is part of the Kelpen Oil products for workshops.
How does the Kelpen Oil laboratory check the fluid?
The Kelpen Oil in-house laboratory in Arujá (SP) analyzes the fluid in use, as a paid service, and tells you whether it is still good or whether it is time to replace the charge. This analysis follows the fluid in use, by the ISO 4008-3 criterion; it does not repeat all the ISO 4113 tests, which apply to new fluid.
| What we measure | What it reveals | Method |
|---|---|---|
| Kinematic viscosity at 40 °C, on the SVM 4001 automatic viscometer | Whether it has passed the discard limit and how far it has moved from the range of new fluid | ASTM D7042 |
| Density | A change that may indicate mixing with diesel or lubricating oil | Measured in the laboratory |
| Water, by the Karl Fischer method (a chemical reaction that counts only the water in the sample) | Moisture condensed in the reservoir | Coulometric Karl Fischer |
| Color, on the standard's ASTM scale | Darkening from oxidation or dirt | NBR 14483 |
| Acidity of the fluid in use, the acid number or TAN (how much acid the fluid has accumulated) | Acids from oxidation; the value is tracked over time and is not compared with the ISO 4113 limit, measured after aging of the new fluid | NBR 14448 |
| Particle count (how many there are of each size) | Dirt that scratches the plunger and clogs the injector hole; the accepted level is the bench maker's, because ISO 4113 sets no limit | ISO 4406 cleanliness code |
The methods are described in how a lubricant analysis laboratory works.
Frequently asked questions
Can I use diesel instead of calibration fluid? Not for calibrating: the measurement loses its reference. S10 diesel can range from 2.0 to 4.5 mm²/s at 40 °C under ANP rules, a much wider range than ISO 4113 fluid. The minimum flash point of diesel is 38 °C, against 75 °C for calibration fluid (both in a closed cup).
What is the difference between ISO 4113 and ISO 4113 CV? CV has the narrower range, which gives more accuracy in adjustment. Viscosity runs from 2.50 to 2.55 mm²/s at 40 °C, against 2.45 to 2.75 for the basic one, and density from 0.8235 to 0.8265 g/mL at 15 °C, against 0.820 to 0.830.
Can I mix in another oil to correct the viscosity of the bench fluid? No. ISO 4008-3 forbids correcting the fluid by mixing: once past the discard limit, the charge is replaced.
Which standard does Keen Fluid FC 4113 meet? ISO 4113-CV-AW. It is indicated for calibrating injection pumps and injectors.
Is ISO 4113 fluid suitable for common-rail injectors? Yes: ISO 4113 fluid is also the reference in testing common-rail injectors, following the procedure of the bench maker and the part maker. Keen Fluid FC 4113 is used in the calibration of common-rail pumps and injectors.
Glossary
AW (anti-wear): version of ISO 4113 with an anti-wear additive.
CV (closer value): version of ISO 4113 with a narrower viscosity and density range.
Delivery: volume the pump or injector supplies over a fixed number of injections.
Density: how much a volume of the fluid weighs, in g/mL.
Designation: the name of the ISO 4113 version that goes on the label, such as ISO 4113-CV-AW.
Flash point: lowest temperature at which the fluid's vapor ignites for an instant with a flame nearby.
Viscosity: a liquid's resistance to flow.
Talk to the Technical Team
The Kelpen Oil Technical Team evaluates the bench, the parts tested, the reservoir volume, the replacement interval and the designation requested, and confirms the suitable product. If the fluid is already in use, the Arujá (SP) laboratory performs the analysis of fluid in use, as a paid service.
Today, check on the bench the designation on the label, the fluid temperature and the date of the last viscosity measurement. Save this article or send it to whoever looks after the bench.
