Marcus Reid

Diesel Technician & Senior Contributor

Marcus spent two decades in independent diesel shops before moving into writing, working mostly on Power Stroke, Cummins and Duramax pickups along with the RVs and farm equipment that came through the same bays. At USA Diesel Finder he covers diagnostics, DPF and emissions systems, and the practical side of choosing a shop — what a fair estimate looks like, which symptoms can wait, and which ones can't. His goal is to give owners enough context to have a confident conversation with their mechanic.

Articles by Marcus Reid

Technician pouring DEF fluid into a diesel truck's exhaust fluid tank at a repair shop
Emissions & DPF
7 min read

What Is DEF? Diesel Exhaust Fluid Explained

DEF fluid is a urea-water solution that cuts NOx emissions from diesel engines. Learn how DEF works with SCR, why your truck needs it, what happens if you run out, and how to store it right.

Mechanic draining a fuel tank after diesel was accidentally put into a gas engine
Maintenance
8 min read

What Happens When You Put Diesel Into a Gas Engine?

Diesel in a gas engine causes rough running, stalling, or a no-start because gas engines rely on spark ignition that diesel can't support. Here's what actually happens, why it differs from gas-in-diesel mistakes, and what fixing it costs.

Mechanic inspecting a turbocharger on a diesel engine to explain whether you can supercharge a diesel instead
Maintenance
7 min read

Can You Supercharge a Diesel? Turbo vs. Supercharger Explained

Yes, you can bolt a supercharger to a diesel — and some classic engines did it from the factory. But here's why almost every modern diesel uses a turbo instead, what changes if you add forced induction, and what it costs to boost a diesel the right way.

What Happens If You Put Gasoline in a Diesel Engine?
Maintenance
7 min read

What Happens If You Put Gasoline in a Diesel Engine?

Gasoline in a diesel engine is a serious misfuel, not a minor mix-up. It strips lubricity from the fuel system and can wreck the injection pump and injectors in minutes. Here's what actually happens, what it costs to fix, and what to do the moment you realize the mistake.

Mechanic performing a fuel filter diesel change on a heavy-duty truck engine in a repair bay
Maintenance
7 min read

How to Change a Diesel Fuel Filter: A Practical Guide

Learn how to change a diesel fuel filter step by step, including tools, priming the system, OEM service intervals, and the warning signs that mean it's overdue. Includes a cost comparison for DIY versus shop service.

Mechanic in work uniform servicing large diesel truck engine in repair shop bay.
Fleet
8 min read

Choosing a Diesel Shop for Your Fleet: What Actually Matters

Picking a fleet diesel repair shop is about more than the nearest bay. Learn what certifications, turnaround times, record-keeping, and downtime math actually separate a shop worth keeping from one that'll cost you miles.

DOT Annual Inspection Checklist: A Fleet Manager's Compliance Guide
Fleet
7 min read

DOT Annual Inspection Checklist: A Fleet Manager's Compliance Guide

A complete DOT annual inspection checklist for fleet managers, built around FMCSA 49 CFR §396.17. Covers required systems, who can sign off, record retention, costs, and how to fold it into your PM program.

Fleet manager reviewing CSA scores and FMCSA inspection reports on a laptop in a truck yard
Fleet
7 min read

CSA Scores Explained: How They Work and What's Changing in 2026

CSA scores decide which fleets get pulled for audits, pay more for insurance, and lose freight contracts. Here's how FMCSA's Safety Measurement System calculates your BASIC percentiles — and what the 2026 methodology changes mean for your operation.

Fleet maintenance technician inspecting diesel truck engine during scheduled preventive maintenance service
Fleet
8 min read

Fleet Preventive Maintenance: Building a Program That Cuts Downtime

A solid fleet maintenance program turns surprise breakdowns into planned shop visits. Here's how to set PM intervals, meet FMCSA record rules, and cut unplanned downtime that eats into your bottom line.