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Oil Level Indicator
Oil Level Indicator (OLI) for Gearboxes, Tanks & Reservoirs
The Esco Oil Level Indicator (OLI) gives maintenance and reliability professionals a clear, 360° view of oil levels inside gearboxes, large tanks, and industrial reservoirs. Built from strong cast acrylic the oil level monitor replaces old-style vented sight gauges that stain, cloud, and fail. Use it as a standalone fluid level indicator or monitor in systems where water contamination is not a concern, or pair it with an Esco Oil Sight Glass at the drain port for complete visual oil inspection.
Where the Oil Level Indicator is used the oil level monitor is suited for any industries relying on rotating or reciprocating machinery with oil reservoirs, including:
- Manufacturing & Industrial Equipment — pumps, gearboxes, conveyors
- Food & Beverage Processing — continuous monitoring without equipment shutdown
- Power Generation — turbines, generators, compressors
- Mining & Aggregate — heavy equipment reservoirs in harsh environments
- Pulp & Paper / Steel Mills — high-demand lubrication management
Frequently Asked Questions About Oil Level Indicators (OLIs)
Q: What is the difference between the Oil Level Indicator and the Oil Sight Glass?
The Oil Level Indicator (OLI) is designed specifically for monitoring oil level and works best in systems where water contamination is not a concern. The Oil Sight Glass — and particularly the Oil Sight Glass & Level Monitor — installs at the drain port and gives you a fuller picture: oil color, clarity, and the ability to drain water contamination before it damages your equipment. If your system needs both level monitoring and contamination visibility, the Oil Sight Glass & Level Monitor is the better fit. Many customers use both products together for a complete visual oil inspection setup.
Q: What sizes does the Esco Oil Level Indicator come in?
The OLI is available in lengths from 3 inches to 15 inches, with part numbers OLI3, OLI6, OLI9, OLI12, and OLI15. Custom lengths are available on request. To find the right size for your application, measure the distance from your equipment's drain port to the maximum height your oil level will reach.
Q: Do I need the optional breather cap?
If your system is open — meaning it is not a closed-loop system — the optional ESBCAP breather cap is strongly recommended. It includes a 2-micron filter that protects your reservoir from airborne contamination and moisture particles. If your system is closed-loop, the top ½" NPT port on the OLI can simply be used as a return connector port back into the system, and no breather is required.
Q: Can the Oil Level Indicator be used in a closed-loop system?
Yes. The OLI has ½" NPT threads at both ends. In a closed-loop configuration, rather than installing a breather cap, you use the top port as a connector port that feeds back into your system. This allows the oil level inside the OLI to equalize with the level inside the reservoir without venting to atmosphere.
Q: What are the temperature and pressure ratings for the OLI?
The OLI is constructed from strong cast acrylic rated for most standard industrial operating conditions. For specific temperature and pressure ratings by size, refer to the specifications and ratings chart on this page. If your application involves elevated temperatures, high pressures, or aggressive chemical environments, contact Esco Products before ordering to confirm the OLI is the right fit.
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Oil Level Indicator
The Oil Level Indicator (OLI) is a is a clear acrylic tube with 1/2” NPT threads at each end for lengths 3” to 15”. Red and green decals are included with the OLI to mark upper and lower limits, or to designate running oil level and idle oil level. It can be installed with the 1/2” ESBCAP optional breathers or if the user requires a closed loop, the 1/2” NPT can be used as a connector port to feed back into the system. See below for product details, specifications, temperature and pressure ratings and size and part number chart.
As low as $45.68Shop Now -
Optional Breather for OLI Sizes 3" - 15"
Esco Breather Cap with 2-micron filter and 1/2” NPT protects from contamination and particles. Recommended for use on the Oil Level Indicators when a closed-loop system is not necessary.
$12.46