AUTOOL AS503 Optical Engine Oil Quality Tester
Original price was: US$66.00.US$39.00Current price is: US$39.00.
- Optical Engine-Oil Screening
- Gasoline + Diesel Oil Modes
- 800 mm PTFE Probe
- Oil Temperature Display
- Optical Engine-Oil Screening: Measure engine-oil transmittance to screen for contamination and suspended particles that reduce transparency.
- Gasoline + Diesel Oil Modes: Choose separate gasoline or diesel engine-oil modes for the intended lubricant check.
- 800 mm PTFE Probe: Reach oil around the engine bay with the flexible, oil-resistant hose probe.
- Oil Temperature Display: View current oil temperature in °C or °F alongside the screening result.
- Status + Sound Prompts: Use screen symbols and sound reminders to distinguish acceptable, attention, and replacement guidance.
- Optical Engine-Oil Screening: Measure engine-oil transmittance to screen for contamination and suspended particles that reduce transparency.
- Gasoline + Diesel Oil Modes: Choose separate gasoline or diesel engine-oil modes for the intended lubricant check.
- 800 mm PTFE Probe: Reach oil around the engine bay with the flexible, oil-resistant hose probe.
- Oil Temperature Display: View current oil temperature in °C or °F alongside the screening result.
- Status + Sound Prompts: Use screen symbols and sound reminders to distinguish acceptable, attention, and replacement guidance.
- 3-Year Warranty Main unit 3 years · Accessories 1 year
- 90-Day Returns Eligible returns within 90 days
- Official Store Genuine products · Direct support
AUTOOL AS503 · Engine Oil Tester with Transmittance Readout
Screen Engine Oil with Temperature Context
Use AS503 to screen engine-oil transmittance and temperature during maintenance. Separate gasoline and diesel modes, an 800 mm PTFE probe, and combined status prompts support quick comparisons under consistent sampling conditions.
- Optical Oil-Transmittance Screen
- Gasoline And Diesel Modes
- 800 mm PTFE Probe
- Oil Temperature Context
- 2.8-Inch Backlit Display
Key Features
Optical Engine Oil Reading with Gasoline and Diesel Modes
High-Precision Optical Probe
The integrated photoelectric transceiver sensor detects engine oil transmittance to help evaluate oil contamination and impurity level.
800mm Flexible PTFE Hose
The 800mm hose probe makes sampling easier around the engine bay. PTFE material resists oil, oxidation, and corrosion for longer service life.
Gasoline And Diesel Modes
Separate gasoline and diesel engine oil modes help users check different lubricant oil standards more accurately.
Oil Temperature Measurement
The built-in temperature sensor displays the actual oil temperature and supports °C / °F switching for easier reading.
2.8-Inch Backlit LCD
The backlit 2.8-inch screen shows battery level, selected engine type, transmittance, oil temperature, and result symbols clearly.
Sound Alarm And Result Reminder
The tester uses screen icons and sound reminders to help users decide whether the oil is acceptable, needs attention, or should be replaced.
Silicone Handheld Grip
The silicone grip supports single-handed operation when checking engine oil.
Battery-Powered Tester
The 175 × 72 × 29mm tester operates on 6V from four 1.5V batteries.
Engine Oil Transmittance
AS503 measures engine oil transmittance in gasoline and diesel modes to support oil condition checks.
Optical Probe Reading
The probe reads light transmission through engine oil and reflects contamination or suspended particles that affect transparency.
3 Years Warranty Support
Main unit: 3-year warranty. Standard accessories: 1-year warranty. Warranty Policy.
Service Workflow
Select the Engine Mode and Sample Correctly
Wipe The Probe
Wipe the test probe clean before use to reduce residue interference.
Remove The Dipstick
Remove the engine oil dipstick or access the engine oil testing point according to vehicle service requirements.
Select Engine Type
Press the engine type selection button to choose gasoline or diesel engine oil mode.
Submerge The Probe
Place the testing probe into the engine oil and make sure the sensing area is properly submerged.
Start The Test
Press the test button and allow the tester to complete the reading process.
Read The Result
The display shows the transmittance percentage, result symbol, and current oil temperature.
Probe-Based Oil Check
Clean the probe, select gasoline or diesel mode, then immerse the probe in the oil and start the test. Read the transmittance and temperature on the display.
Safe Use
Treat the Score as a Screening Result
Engine Oil Only
AS503 is intended for gasoline and diesel engine lubricating oil. It is not a brake fluid, transmission fluid, or power steering fluid tester.
Optical Detection Limit
Because AS503 uses an optical detection probe, it is not suitable for engine oils containing molybdenum disulfide (MoS₂), organic molybdenum, graphene, or similar additives.
Suzuki J20A Not Supported
AS503 does not support the Suzuki J20A engine. Contact AUTOOL Store before ordering if this engine is your intended application.
Check Oil Additives
Do not use AS503 with oils containing molybdenum disulfide, organic molybdenum or graphene additives.
Recommended Check Interval
Use AS503 as a reference check every 5,000-10,000 km, depending on engine condition, oil type, driving environment, and maintenance schedule.
Interpret Engine Oil Transmittance in Context
Select only a listed fluid and use a clean, representative sample. The condition score is the tester’s screening output, not a direct measurement of viscosity, wear metal, contamination species or remaining service life.
Model Comparison
Choose the Right Fluid Test Method
Model Guide
Choose one or more models. AS503 is selected by default.
| Product name | AS501 Brake Fluid Tester | AS502 Brake Fluid Tester | AS503 Engine Oil Quality Tester | AS505 Transmission Fluid Tester | AS506 Brake Fluid Boiling Point Tester | AS507 Power Steering Fluid Tester | AS509 Coolant Boiling Point Tester |
|---|---|---|---|---|---|---|---|
| Test Method & Application | |||||||
| Detection Technology | Pressure Boost Detection Technology | Water-content screening; no hydraulic pressure generation or measurement | Optical Probe Technology | Optical Probe Technology | Sample Heating Technology | Optical Probe Technology | Sample Heating Technology |
| Operating Principle | Brake Fluid (Water Content) | Brake Fluid (Water Content) | Engine Oil (Transmittance) | Transmission Fluid(Transmittance) | Brake Fluid (Boiling Point) | Steering Fluid (Transmittance) | Coolant |
| Test Mode Selection | Normal Mode | Normal Mode/Expert Mode | Gasoline Engine/Diesel Engine | Automotive Transmission Fluid | Normal Mode/Brand Mode | Automotive Steering Gear | Normal Mode/Brand Mode |
| Boiling Point Reference Value | × | × | × | × | ✓ | × | ✓ |
| Normal Mode | 6 Types ENV-4、ENV-6 DOT3、DOT4、DOT5、DOT5.1 | 3 Types DOT3、DOT4、DOT5.1 | × | × | DOT3, DOT4 and DOT5.1 (procedure-confirmed selections) | × | 23 Coolant Brands For ACDELCO、BASF、BOSCH、CASTROL、ENGINE_ICE、EVANS、FORD、HONDA、JOHN_DEERE、KUNLUN、MOBIL、MOPAR、NISSAN、OMTECH、PEAK、PRESTONE、RECOCHEM、SHELL、SKI-DOO、ZEREX、STAR_BRITE、TOTAL、TOYOTA |
| Measurement & Response | |||||||
| Temperature Unit Switching | × | × | ℃/℉ | ℃/℉ | ℃/℉ | ℃/℉ | ℃/℉ |
| Temperature Measurement Range | × | × | 0-85℃ 0-185℉ | 0-85℃ 0-185℉ | 0-320℃ 0-608℉ | 0-85℃ 0-185℉ | Diluted Coolant Boiling Point Range： 100°C~120°C(212°F~248°F) Original Manufacturer Coolant Boiling Point Reference Range 106°C~191°C(221°F~376°F) |
| Test Duration | 10s Response | 10s Response | 10s Response | 10s Response | 16s Response | 10s Response | 20~40s Response |
| Display, Probe & Power | |||||||
| Backlit Display Screen | 1.8-inch | 2.8-inch | 2.8-inch | 2.8-inch | 1.54-inch | 2.8-inch | 1.6-inch |
| Test Cable Length | 26cm | 26cm | 80cm | 80cm | 4cm | 80cm | 130cm |
| Power Supply Voltage | 3V | 6V | 6V | 6V | 12V | 6V | 10-14V |
| Hose Material | Iron Oxide | 304 Stainless Steel | Teflon | Teflon | × | Teflon | × |
Manual & Support
Find the Manual and Fluid-Test Guidance
AUTOOL AS503 User Manual
Open the PDF manual for AUTOOL AS503 gasoline and diesel oil testing, optical-probe use, temperature measurement, result interpretation, cleaning, safety and troubleshooting support.
Package Contents
See What Comes in the Box
- Main UnitAUTOOL AS503 engine oil quality tester with integrated flexible probe
- ItemProbe Built-in 800mm PTFE / Teflon hose probe
- DocumentationUser manual
- PackageAS503 retail box
- ItemPower Requirement Requires 4 × 1.5V batteries; inclusion should follow the final package listing
Buyer Questions
Fluid Fit, Method and Result Questions
What Does The AUTOOL AS503 Test?
AS503 tests gasoline and diesel engine lubricating oil by checking oil transmittance with an optical probe. It also displays the current oil temperature to help users evaluate engine oil condition during maintenance.
Can AS503 Test Both Gasoline And Diesel Engine Oil?
Yes. AS503 supports separate gasoline engine and diesel engine oil mode selection. Select the correct engine type before starting the test.
How Should I Read The Transmittance Result?
- When transmittance is between 100% and 50%, oil replacement is generally not required.
- When it is between 50% and 30%, the screen shows a warning symbol.
- When it drops below 30%, the tester beeps and suggests immediate oil replacement.
- Use the result together with actual vehicle service requirements.
Which Engine Oils Are Not Suitable For AS503?
AS503 relies on optical detection, so it is not suitable for engine oils containing molybdenum disulfide (MoS₂), organic molybdenum, graphene, or similar substances. These additives may affect optical analysis results.
Does AS503 Support Suzuki J20A Engine Testing?
No. AS503 does not support the Suzuki J20A engine. Contact AUTOOL Store for compatibility help with another model or engine.
How Often Should I Test Engine Oil?
A practical reference is to check engine oil every 5,000-10,000 km, depending on oil type, driving conditions, vehicle age, engine condition, and the maintenance schedule recommended for the vehicle.
What Batteries Does AS503 Use?
AS503 uses 6V power from 4 × 1.5V batteries. Battery inclusion should follow the final package listing, so do not assume batteries are included unless confirmed.
What Should I Do If The Hose Or Probe Gets Stuck?
Do not force the hose or probe out if it becomes jammed. Stop operation, check the surrounding position carefully, and contact support if you are unsure how to remove it safely.
What Is Included In The Box?
Package contents: AS503 main unit with integrated flexible probe, user manual, and retail box. AS503 requires 4 × 1.5 V batteries; battery inclusion follows the selected package listing.
What Is The Difference Between AS503 And Other AUTOOL Fluid Testers?
- AS503 is for gasoline and diesel engine oil transmittance testing.
- AS501 and AS502 are brake fluid water content testers.
- AS505 is for transmission fluid transmittance.
- AS506 is a brake fluid boiling point tester.
- AS507 is for power steering fluid transmittance.
How Long Is The Warranty?
Main unit: 3-year warranty. Standard accessories: 1-year warranty. Warranty Policy.
Can AS503 Replace Professional Oil Laboratory Analysis?
AS503 provides quick oil-transmittance and temperature checks for maintenance screening. Use professional oil analysis when chemical composition or wear-metal data is required.
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It looks like it works!
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I compared it with other brands' testers, and it delivers accurate results with…
I compared it with other brands’ testers, and it delivers accurate results with fast detection speed. The product feels premium and is very easy to use.
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