middletown ct generator parts service maintenance stewart stevenson

Middletown, CT
Products, Services & Capabilities

The core capability of Stewart & Stevenson Atlantic Division is the sale and expert service of diesel and alternative fuel engines, transmissions, power generation systems and a wide range of related products, components, parts and accessories. You’ll find our products hard at work in trucks, buses, ferry and commercial marine applications, and pleasure-craft, as well as in governmental, financial and medical environments where ongoing power supply is critical.

Stewart & Stevenson Atlantic Division represents the most respected brands in the business—names like: Detroit Diesel®, MTU®, Mercedes-Benz®, Allison Transmission® and more. We also provides comprehensive service for a variety of equipment in both On-Highway and Off-Highway markets: medium- and heavy-duty trucks, buses and coaches; fire and emergency vehicles; power generation systems; marine propulsion and support equipment (for both commercial vessels and pleasure-craft); and construction and industrial machinery.

Middletown Branch
300 Smith Street
Middletown, CT 06457
Phone: (800) 521-3499
Rental Contact: View the Middletown Rental Page

Stewart & Stevenson Atlantic Division
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Stewart & Stevenson Atlantic Division represents the most respected brands in the business—names like: Detroit Diesel®, MTU®, Mercedes-Benz®, and more. Transmissions Allison Transmission, Inc. (Allison) is the premier global provider of commercial duty automatic transmissions and hybrid propulsion systems.



Standby Diesel
A complete line of critical power systems from MTU Onsite Energy. Diesel Standby, Emergency & Prime power generator sets from 27 – 3,250 kWe, ATS switches from 30 – 4,000 amps.

Continuous Gas
Low emissions Standby & Prime power gaseous-fueled generator sets from MTU Onsite Energy ranging from 30 kW – 400 kWe.

Standby Gas
Highly efficient Continuous Gas power modules from MTU Onsite Energy in 350 – 2,145 kWe ratings provides a constant flow of power with the ability to operate in grid parallel or grid independent mode.

Also known as Combined Heat & Power (CHP), MTU Onsite Energy offers a pre-engineered systems with integrated heat recovery in an attractive package. Systems range from 125 – 2,000 kWe and can operate on natural and biogas.


In the rivers and open seas of the Atlantic Northeast, Stewart & Stevenson Atlantic Division is the recognized leader and premium sales and after-sales provider of MTU marine propulsion and auxiliary power systems. Our range of systems powers commercial workboats, commuter ferries and pleasure craft.


Engineered Power Units
Custom Repowers for The C & I Marketource for MTU engineered Power Drive Units available from 101HP to 3000HP to fit stationary and mobile equipment applications.

Custom Repowers
Stewart & Stevenson Atlantic Division is your source for custom re-powers for competitive engines or your older but always dependable Detroit Diesel 2 cycle engines.

Engine Selection Assistance
Buying a new piece of equipment today is costly. APS can assist you with the selection for all OEM’s using MTU engines/Allison Transmission in equipment you are considering in your purchasing process.

Exhaust After Treatment
Clean air! We all want to do our part to make the environment better for everyone. At APS we offer the latest selection in exhaust emission after treatment devices for all engines and equipment types.


There’s no substitute for experience! At Stewart & Stevenson Atlantic Division we have factory certified technicians with hundreds of years of combined power generation experience available 7 days a week, 24 hours a day in any emergency situation. Contact us for:

  • Emergency and Field Services
  • Shop Services
  • Emission compliance and abatement
  • On-site testing
  • Field Services


Operating one of the most extensive parts departments in the industry, Stewart & Stevenson Atlantic Division stocks more than $25 million in quality parts. That means we’ll have the part you need when you need it.

The WheelTime promise, combined with the finest quality parts and our service excellence, assures the best possible customer experience.

All Makes
Stewart & Stevenson Atlantic Division is authorized to carry the best parts in the business. We service your vehicle from bumper to pumper which include:

  • Accessories & Chemicals
  • Brake & Wheel End
  • Cab & Hood
  • Chassis & Suspension\
  • Drivetrain
  • Engine & Exhaust
  • Lighting & Electric
  • Steering & Axle


Clean air! We all want to do our part to make the environment better for everyone. At Stewart & Stevenson Atlantic Division we offer the latest in exhaust after-treatment devices for all engine types. We are authorized representatives for Donaldson, Johnson-Matthey, Rypos and Cleaire Advanced Emission Controls. We offer closed crankcase ventilation systems, diesel oxidation catalysts, diesel particulate filters, NOx abatement systems and hybrid particulate systems to meet current and future emission requirements. We offer emission testing, maintenance and documentation services designed to ease the ever-increasing burden of regulatory compliance for our customers. Call us today and find out how we can help you meet tomorrow’s stringent emission requirements today.