Autool AS503 | Engine Oil Tester
Warranty directly via AsTools
Warranty directly via AsTools
We handle warranty cases ourselves, quickly and without involving the manufacturer. Thanks to our own parts inventory and technical expertise, we can usually assist you immediately. Only in exceptional cases do we still send the product to the supplier.
2 years warranty on all products
2 years warranty on all products
All our products come with a 2-year factory warranty. This ensures you long-lasting quality and service.
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Easy returns
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Professional customer service
Professional customer service
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The Autool AS503 is an engine oil condition tester. It assesses how contaminated the engine oil is. An optical probe measures how much light can still pass through the oil; the more soot and wear particles present, the less light gets through.
This transforms an oil change into a decision based on measured data rather than mileage. The probe is fitted with an 800 mm PTFE hose, allowing you to access the oil via the dipstick tube without removing any components. Separate settings are provided for petrol and diesel engine oils, and the tester also reads oil temperature. Assessment follows three levels: above 60 per cent indicates good condition, between 60 and 30 per cent triggers a warning, and below 30 per cent means replacement is needed.
KEY BENEFITS
POINTS TO NOTE
Application and functionality
Engine oil degrades under load, not over time. Soot, combustion residue and wear particles make the oil progressively more opaque, and it is precisely this light transmittance that is measured here. This means an oil change decision rests on the actual condition of the oil rather than on mileage intervals.
The Autool AS503 supports the following measurement and configuration functions:
- Optical measurement of light transmittance: determines how much light passes through the oil as an indicator of particulate content.
- Two oil settings: separate modes for petrol and diesel engine oils, which naturally darken at different rates.
- Assessment in three levels: Above 60 per cent is good, between 60 and 30 per cent triggers a warning, below 30 per cent indicates replacement is needed.
- Temperature measurement: displays oil temperature alongside the measured data.
- Unit selection: Temperature in degrees Celsius or Fahrenheit.
- Backlight: can be switched on and off with a dedicated button.
What you see on the display
- Light transmittance: The measurement result as a percentage, with an analogue bar alongside.
- Assessment: Above 60% is good, between 60% and 30% gives a warning, below 30% recommends replacement.
- Fluid temperature: In degrees Celsius or Fahrenheit, switchable with a dedicated button.
- Battery level: So you do not run out of power mid-inspection.
How to use it
- Insert the batteries: Four AAA in the compartment on the rear, observing correct polarity.
- Allow the engine to cool below 60 °C: Then wipe the probe clean and dry.
- Select the oil type: Petrol or diesel, using the selection button.
- Remove the dipstick and insert the probe: Guide it through the dipstick tube into the oil.
- Press the test button and read the result: After ten seconds, transmittance, condition assessment and oil temperature appear on the display.
Special features and capabilities
Two factors determine whether this measurement is reliable: the probe length and the oil composition.
- 800 mm PTFE hose probe: resistant to oil, oxidation and corrosion, and long enough to reach the sump via the dipstick tube.
- Not suitable for particle additives: oils containing MoS2, organic molybdenum or graphene carry particles themselves and interfere with optical measurement.
- Measurement below 60 degrees: the manual specifies that the engine must be below this temperature when taking measurements.
Where to use it
The measurement is deployed where the service interval does not align with actual usage patterns, and where the oil's condition should determine the replacement decision.
- If interval timing is uncertain: Short journeys and urban driving stress the oil harder than the odometer suggests.
- For a vehicle with unknown service history: A test on arrival reveals whether the oil has genuinely been changed recently.
- For a fleet of lease or company vehicles: To establish which units need servicing ahead of the scheduled interval.
- Following an engine problem: To assess how heavily the oil has become contaminated.
Package contents
- 1x Autool AS503 engine oil condition tester with 800 mm probe hose
- 1x User manual
Technical specifications
| Specification | Description |
|---|---|
| Brand | Autool |
| Model | AS503 |
| Type | Engine oil condition tester, optical |
| Measurement principle | Optical probe measuring oil light transmittance |
| Measurement value | Light transmittance as a percentage, plus oil temperature |
| Assessment | Above 60% good, 60% to 30% warning, below 30% replace |
| Settings | Petrol engine oil and diesel engine oil |
| Response time | Ten seconds |
| Display | 2.8-inch LCD with backlight |
| Probe | Flexible 800 mm PTFE hose |
| Not suitable for | Oil containing MoS2, organic molybdenum or graphene |
| Power supply | 6V, four AAA batteries |
| Operating temperature | −10 °C to +60 °C |
| Auto shut-off | After five minutes of inactivity |
| Dimensions | 175 × 72 × 29 mm |
| Article number | AS503 |
