Screen Gasoline and Diesel Engine Oil by Transmittance and Temperature
The AS503 dips an optical probe into engine oil, reads how much light passes through it and shows the result with the current oil temperature, in separate gasoline and diesel modes. Not suitable for oils with molybdenum or graphene additives.
- Gasoline + Diesel Modes
- 800 mm PTFE Probe
- Transmittance + Temperature
- Sound Alarm
- 2.8-Inch Backlit LCD
Key Features
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Optical Oil Probe
An integrated photoelectric transceiver sensor reads transmittance, which drops with contamination and suspended particles.
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Flexible PTFE Hose
Makes sampling easier around the engine bay and resists oil, oxidation and corrosion.
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Gasoline and Diesel Modes
Select the engine type before testing to match the lubricant standard.
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Oil Temperature Readout
A built-in sensor shows the actual oil temperature, switchable between °C and °F.
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Clear Screen and Alerts
Battery level, engine type, transmittance, temperature and result symbols on one screen, with a beep when replacement is suggested.
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One-Hand Grip
A silicone grip supports single-handed checks.
What’s in the Box
- AS503 engine oil quality tester with integrated 800 mm PTFE probe
- User manual
- Retail box
How to Use
- Wipe the probeClean the test probe to reduce residue interference.
- Open the test pointRemove the dipstick or access the oil test point per the vehicle service requirements.
- Select the engine typeChoose gasoline or diesel mode with the selection button.
- Submerge the probePlace the probe in the oil with the sensing area fully immersed.
- Start the testPress the test button and let the reading complete.
- Read the resultCheck transmittance, result symbol and oil temperature on the display.
Modes, results and cleaning: AS503 user manual (PDF).
Good to Know
Caution
- Not suitable for engine oils containing molybdenum disulfide (MoS₂), organic molybdenum, graphene or similar additives.
- The Suzuki J20A engine is not supported.
- For engine oil only; it is not a brake, transmission or power steering fluid tester.
- Batteries are not confirmed as included; prepare four 1.5 V batteries.
- If the hose or probe jams, do not force it out; stop and check its position.
Care
- Clean the probe before each test and use a clean, representative sample.
- A check every 5,000–10,000 km is a practical reference, depending on oil type, driving conditions and maintenance schedule.
- The result is a screening reference, not laboratory analysis of viscosity, wear metals or remaining service life.
FAQ
Which AUTOOL tester do I need for other fluids?
AS501 and AS502 test brake fluid water content, AS505 transmission fluid transmittance, AS506 brake fluid boiling point and AS507 power steering fluid transmittance.
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