Diesel Opacity Testing Near San Francisco: What Fleet Owners Need to Know
If you run a diesel truck, bus or motorhome with a 2012 or older engine in California, it needs a smoke opacity test and a visual inspection to stay compliant with CARB's Clean Truck Check program. In San Francisco and across the Bay Area, the fastest way to get diesel opacity testing done is mobile testing: a tester comes to your yard, jobsite or parking spot, runs the test on site and submits the results to CARB, so your vehicles never leave the area where they work.
Here is what the test involves, which vehicles need it and how to keep your fleet on schedule.
What is a diesel opacity test?
A diesel opacity test measures how much smoke comes out of the exhaust. The tester connects an opacity meter to the exhaust and follows the SAE J1667 procedure, a standard "snap acceleration" test: the engine is revved quickly from idle several times while the meter measures how much light the smoke blocks. Less smoke means a healthier engine and emissions system.
For Clean Truck Check, the opacity test comes with a visual inspection of the vehicle's emissions control equipment, so both parts are completed in the same visit.
Which vehicles need opacity testing?
The test your vehicle needs depends mainly on the engine model year:
Diesel, 2013 or newer: OBD test (reads the engine's onboard diagnostics)
Diesel, 2012 or older: smoke opacity test plus visual inspection
That means older trucks, buses, diesel motorhomes and equipment haulers are the vehicles most likely to need opacity testing. Many Bay Area fleets have a mix of both, and a mobile tester can handle OBD and opacity vehicles in the same visit.
How often do you need to test?
Most heavy-duty vehicles covered by Clean Truck Check currently test twice a year, while California-registered diesel motorhomes and agricultural vehicles test once a year. Your exact deadlines appear in your CARB Clean Truck Check account, and missing one can lead to a DMV registration hold, so it pays to track them ahead of time.
How mobile opacity testing works
Confirm which vehicles are due. Share your vehicle list or let us check your CARB account to see upcoming deadlines.
Schedule around your operation. We come to your yard, jobsite or facility at a time that keeps your trucks working.
Test on site. We run the SAE J1667 opacity test and the visual inspection right where the vehicle is parked.
Submit to CARB. Results go straight into the Clean Truck Check system, and we track your next deadline.
No driving trucks across the Bay to a test lane, no lost hours in traffic, and no extra trips for your drivers.
What if a vehicle does not pass?
If a vehicle does not pass, we explain why and what usually needs attention before the retest, such as maintenance on the emissions control system. Once the issue is addressed, we provide the retest at no additional charge.
Diesel opacity testing across the Bay Area
We test at your location in San Francisco, Oakland, San Jose, Berkeley, Alameda, Emeryville, Hayward, Daly City, San Mateo, Concord, Livermore, Fairfield, Petaluma and surrounding cities, and support fleets with vehicles anywhere in California.
Frequently asked questions
Do I need to bring my truck to a testing station?
No. With mobile opacity testing, the tester comes to you and completes the test where your vehicle is parked.
Can you test OBD and opacity vehicles in the same visit?
Yes. Mixed fleets are common, and we test both types during the same appointment.
Do diesel motorhomes need opacity testing?
If the motorhome has a 2012 or older diesel engine, it generally needs an opacity test and visual inspection. California-registered diesel motorhomes test once a year.
How do I know which test my vehicle needs?
Check the engine model year: 2013 or newer usually means OBD, 2012 or older usually means opacity. Not sure? Send us the engine year or VIN and we will tell you.
Get your fleet tested without the downtime
Bay Area Diesel Testing provides mobile opacity and OBD testing, remote testing and CARB account management for fleets across California. Request a quote or call 415-965-9330 to schedule testing at your location.
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