The AUTOOL AS503 is a handheld engine oil tester for gasoline and diesel vehicles. It uses optical probe technology to check engine oil transmittance and oil temperature, helping users evaluate oil contamination, oil quality, and replacement timing during automotive inspection and maintenance.
Engine Oil TransmittanceGasoline / Diesel ModesOil Temperature Display10s Response
2.8-inchBacklit LCD
800mmPTFE Probe Hose
6V4 × 1.5V Batteries
3 YearsWarranty Support
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Before You Order And Use
Before You Order And Use
AS503 is designed for engine lubricating oil quality checks based on light transmission. Review the oil type limitation, engine limitation, test interval, and probe handling notes before ordering or using the tester.
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 Suzuki J20A engine testing for the time being. Contact support before ordering if you need confirmation for this engine.
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.
Probe Handling Reminder
Do not force the hose or probe out if it becomes jammed.
Wipe the probe clean before and after testing to reduce residue interference.
Use the result as a maintenance reference together with actual oil condition and vehicle service requirements.
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Key Features
Key Features
AS503 combines optical oil transmittance detection, oil temperature measurement, gasoline and diesel mode selection, a flexible PTFE probe hose, a backlit LCD, sound reminders, and a handheld body for quick engine oil checks.
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.
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Measurement And Reading Guide
Measurement And Reading Guide
Engine oil supports lubrication, cooling, rust prevention, cleaning, sealing, and buffering. AS503 gives a fast reference reading by checking oil transmittance and oil temperature, helping users decide when oil maintenance may be needed.
Optical Probe Reading
The probe reads light transmission through engine oil and reflects contamination or suspended particles that affect transparency.
100%-50%
When transmittance is between 100% and 50%, the tester generally indicates that oil replacement is not required yet.
50%-30%
When transmittance falls between 50% and 30%, the display shows a warning symbol to remind users to consider oil replacement.
Below 30%
When transmittance drops below 30%, the tester beeps and suggests replacing the engine oil as soon as possible for safety.
Reading Note
The AS503 result is a maintenance reference and should be considered together with mileage, oil type, engine condition, and service requirements.
Oil temperature is shown with the T indicator and can be switched between °C and °F.
AUTOOL AS503 has CE, FCC, and RoHS certifications and is designed for automotive aftermarket inspection and maintenance use.
How To Use
How To Use
Use the AS503 probe directly with engine oil, select the correct gasoline or diesel mode, and read the transmittance and oil temperature result after the test starts.
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.
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Use Notes
Select the correct gasoline or diesel mode before testing.
Do not force the hose or probe if it is stuck during removal.
Clean the probe after testing to protect measurement accuracy and product life.
Specifications
AUTOOL AS503 Product Specifications
AS503 is a 6V handheld engine oil quality tester with optical probe technology, 80cm PTFE test cable, 2.8-inch LCD screen, gasoline and diesel mode selection, and 10-second response time.
Detection
Product
AUTOOL AS503 Engine Oil Quality Tester
Detection Technology
Optical probe technology
Operating Principle
Engine oil transmittance
Supported Oil Type
Gasoline and diesel engine lubricating oil
Test Mode Selection
Gasoline engine / diesel engine
Test Duration
10s response
Display And Reading
Display
2.8-inch backlit LCD
Reading
Engine oil transmittance percentage, oil temperature, result symbols, battery level, backlight, and sound indicator
Temperature Unit
°C / °F switchable
Oil Temperature Measurement Range
0-85°C / 0-185°F
Probe And Body
Test Cable Length
80cm
Hose Material
PTFE / Teflon
Body Design
Handheld body with silicone grip area for single-hand operation
Dimensions
175 × 72 × 29mm
Power And Environment
Operating Voltage
6V, 4 × 1.5V batteries
Operating Temperature
-10°C-60°C
Certifications
CE, FCC, RoHS
Warranty
3-year warranty support for eligible non-human damage cases
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Detection
ProductAUTOOL AS503 Engine Oil Quality Tester
Detection TechnologyOptical probe technology
Operating PrincipleEngine oil transmittance
Supported Oil TypeGasoline and diesel engine lubricating oil
Test Mode SelectionGasoline engine / diesel engine
Test Duration10s response
Display And Reading
Display2.8-inch backlit LCD
ReadingEngine oil transmittance percentage, oil temperature, result symbols, battery level, backlight, and sound indicator
Temperature Unit°C / °F switchable
Oil Temperature Measurement Range0-85°C / 0-185°F
Probe And Body
Test Cable Length80cm
Hose MaterialPTFE / Teflon
Body DesignHandheld body with silicone grip area for single-hand operation
Dimensions175 × 72 × 29mm
Power And Environment
Operating Voltage6V, 4 × 1.5V batteries
Operating Temperature-10°C-60°C
CertificationsCE, FCC, RoHS
Warranty3-year warranty support for eligible non-human damage cases
Product Comparison
Product Comparison
Compare AS503 with other AUTOOL oil and fluid analyzers before choosing the right tester for engine oil, brake fluid, transmission fluid, brake fluid boiling point, or power steering fluid.
AS503 FocusEngine oil quality tester for gasoline and diesel engine oil transmittance with 2.8-inch LCD, 80cm PTFE cable, 6V power, °C / °F switching, and 10s response.
Brake Fluid Water ContentAS501 and AS502 are brake fluid testers based on pressure boost detection technology for water content checks.
Boiling Point TestingAS506 is a brake fluid boiling point tester using flash point heating technology and 12V power.
Power Steering FluidAS507 is designed for automotive steering gear power steering fluid transmittance checks.
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Related Products
Related Products
Compare related AUTOOL testers for brake fluid water content, engine oil quality, transmission fluid, brake fluid boiling point, and power steering fluid before choosing the right model.
Select options
This product has multiple variants. The options may be chosen on the product page
Select options
This product has multiple variants. The options may be chosen on the product page
Manual And Downloads
Manual And Downloads
Download the AS503 user manual for operating steps, button functions, gasoline and diesel mode selection, oil transmittance reading, temperature display, and safe-use instructions.
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AUTOOL AS503 User Manual
Open the PDF manual for AS503 setup, engine type selection, testing operation, display symbols, and maintenance guidance.
Contact AUTOOL Store before ordering if you need to confirm oil compatibility, Suzuki J20A limitation, MoS₂ / graphene oil limitation, battery setup, or AS series model selection.
The package image shows the AS503 main unit, retail box, and user manual. Batteries are required for operation, but do not assume batteries are included unless confirmed by the final package listing.
Main UnitAUTOOL AS503 engine oil quality tester with integrated flexible probe
ProbeBuilt-in 800mm PTFE / Teflon hose probe
DocumentationUser manual shown in the package image
PackageAS503 retail box shown in the package image
Power RequirementRequires 4 × 1.5V batteries; inclusion should follow the final package listing
Questions And Answers
These answers cover AS503 test function, gasoline and diesel modes, transmittance result reading, unsuitable oil additives, Suzuki J20A limitation, test interval, power supply, probe handling, package contents, and warranty support.
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.
Yes. AS503 supports separate gasoline engine and diesel engine oil mode selection. Select the correct engine type before starting the test.
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.
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.
No. AS503 does not support Suzuki J20A engine testing for the time being. Please contact AUTOOL Store before ordering if you need model or engine compatibility confirmation.
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.
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.
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.
Refer to the Packing List image for the final package contents. The image shows the AS503 main unit with integrated flexible probe, user manual, and retail box. AS503 requires 4 × 1.5V batteries; battery inclusion should follow the final package listing.
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.
AUTOOL provides 3-year warranty support for eligible non-human damage cases. For damage caused by non-human factors, AUTOOL may provide replacement parts within the warranty policy. Contact support for setup, compatibility, package, or troubleshooting help.
No. AS503 is a practical automotive maintenance reference tool for quick oil transmittance and temperature checks. For detailed chemical composition, wear metal analysis, or laboratory-grade diagnosis, use professional oil analysis services.
Warranty And Contact
Warranty And Contact
For AS503 oil compatibility, Suzuki J20A limitation, MoS₂ / graphene additive limitation, battery setup, result interpretation, probe handling, package confirmation, warranty, or AS series model selection, contact AUTOOL Store directly.
Pre-Sales And Product Support
Use support if you need help confirming whether AS503 is suitable for your engine oil, vehicle, or maintenance scenario. AUTOOL support can also help with AS502 / AS503 / AS505 / AS506 / AS507 model selection and package confirmation.
3-year warranty support for eligible non-human damage cases
Oil compatibility and additive limitation confirmation
Suzuki J20A engine limitation confirmation
Battery setup and display symbol explanation
Probe handling and stuck hose guidance
Package contents and AS series model comparison support
Customer support response as soon as possible, generally within 24 hours
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