Your engine oil isn’t just a lubricant. It plays a critical role in protecting your engine by reducing friction, controlling heat, and preventing wear on internal parts. Over time, though, oil can break down or become contaminated. When that happens, it stops protecting your engine and can begin to damage it.
If you’ve noticed a burning smell, strange noises after startup, or sluggish performance, your oil may already be doing more harm than good. In this post, we’ll walk through five clear warning signs that it’s time to take a closer look, especially if you drive a diesel truck like a PowerStroke, Cummins, or Duramax. You’ll also learn how these signs show up differently in diesel engines and what you can do to prevent major repairs.
At FloState Auto Diesel Repair, we’re here to help you protect your engine and extend its life with expert service and honest advice.
1. You Smell Burning Oil
A burning oil smell is never normal. If you catch a whiff of something bitter and smoky when your truck is idling or right after you shut it off, that’s a red flag.
Why it matters: Burning oil can mean that your oil is leaking onto hot engine components like the exhaust manifold. But it could also be a sign that your oil is too old, too thin, or has lost its protective additives. Either way, your engine isn’t being protected the way it should be.
Real-world example: Many diesel truck owners come to us because they’ve noticed a burnt smell after long hauls. Often, the oil has thinned out due to prolonged heat exposure and needs to be changed, especially in Florida’s hot climate.
2. You Hear a Ticking or Knocking Noise After Startup
Engines make some noise, but a distinct ticking or knocking sound right after startup is a serious warning sign. It usually means your engine oil isn’t circulating quickly enough, or it has degraded to the point where it can no longer protect internal components.
Why it matters: If you’re hearing this type of noise, it’s likely more than just an overdue oil change. Your engine may already be experiencing wear from a lack of lubrication. Diesel engines like PowerStroke, Cummins, and Duramax depend on high-pressure oil systems. When oil is too thin, dirty, or broken down, parts like lifters, bearings, and camshafts may be running with little to no protection during startup. That early wear adds up fast.
What we recommend: Schedule a diagnostic oil service right away. At FloState Auto Diesel Repair, we go beyond a basic oil change. Our technicians check for signs of damage, test oil pressure, and use high-quality synthetic and blend oils that protect your diesel engine from the moment you start it. This kind of issue won’t fix itself, and the sooner we catch it, the better your chances of avoiding major repairs.
3. The Oil on Your Dipstick Is Dark, Thick, or Sludgy
Checking your dipstick is one of the easiest ways to gauge your engine’s health. Clean oil should be amber or light brown. If it’s thick, black, or has a tar-like consistency, that’s a problem.
Why it matters: Dirty oil clogs passages and reduces lubrication. It also loses its cooling ability and can cause heat to build up inside the engine, especially in turbo diesels.
Every oil change at FloState Auto Diesel Repair includes a courtesy inspection, and we routinely check and top off fluids to help catch problems before they turn into costly repairs.
4. You’re Noticing Poor Performance or Increased Fuel Consumption
Has your diesel truck lost some of its usual power? Are you making more trips to the fuel pump than normal? These symptoms often mean your engine is no longer running efficiently, and degraded oil could be a contributing factor.
Why it matters: When engine oil begins to break down, it creates more internal resistance. Your engine has to work harder to deliver the same performance, which leads to higher fuel consumption and unnecessary strain on vital components. If you’re noticing a drop in fuel economy or power, your oil may have already lost its ability to lubricate and protect effectively.
Diesel-specific note: In diesel engines like Cummins, Duramax, and PowerStroke, oil quality directly affects the performance of turbochargers and fuel injectors. These components rely on clean, stable oil to function properly. Contaminated or worn-out oil can reduce boost pressure, interfere with injector timing, and cause long-term wear. Regular oil service is essential to keep your diesel engine performing the way it should.
5. Your Oil Change Light Comes On, Or It’s Just Been Too Long
Modern vehicles are smart enough to tell you when it’s time for maintenance. If your oil change light comes on, don’t ignore it.
Why it matters: Ignoring oil change intervals can lead to thickened oil, sludge buildup, and internal damage, especially for diesel trucks working under heavy loads.
Rule of thumb: For light-duty diesel trucks, we recommend changing the oil every 5,000 to 7,000 miles, depending on your usage. Severe service (towing, off-road, or extreme heat) means you should consider even shorter intervals.
What Dirty or Worn Oil Does to Your Engine
If your oil isn’t clean and fresh, the consequences go far beyond a simple filter replacement. When engine oil loses its ability to lubricate and cool effectively, even everyday driving can start to wear down your engine. This is especially true for diesel trucks, where added heat and pressure push oil to its limits. Here’s what can happen when you keep running on dirty, worn, or broken-down oil:
Increased engine friction
Without the proper lubrication, metal components inside your engine rub directly against each other. This increases wear and tear on crucial parts like camshafts, pistons, and bearings, speeding up the aging of your engine.
Excessive heat buildup
Fresh oil helps regulate internal temperatures. But when oil is old or dirty, it can no longer absorb and dissipate heat effectively. The result? Overheating puts stress on every system in your engine.
Turbo failure in diesel engines
Your turbocharger spins at extremely high speeds and relies on clean, fast-moving oil to function. Contaminated oil can clog turbo oil lines or reduce flow, causing failure that could cost thousands to fix.
Clogged oil passages
Thick, sludgy oil doesn’t flow the way it should. Over time, it can clog narrow oil passages, starving parts of your engine of the lubrication they need. This type of blockage is a silent killer for engine performance.
Poor fuel economy
When your engine has to work harder due to excess friction or heat, it burns more fuel. Dirty oil increases resistance within the engine, which directly impacts efficiency and mileage.
Permanent engine wear
The longer bad oil circulates through your engine, the more damage it does. Once key parts begin to wear down or fail, repairs often mean major overhauls or even full replacements.
At FloState Auto Diesel Repair, we’ve seen it all. Many of our diesel clients come in with these exact issues, and most of them started with something simple: neglecting their oil change. Regular maintenance and high-quality oil are the best defense against long-term engine damage, especially in hardworking diesel trucks.
What Makes FloState the Right Choice for Your Oil Change
Choosing where to get your oil changed isn’t just about convenience; it’s about trust, expertise, and long-term engine protection. At FloState Auto Diesel Repair, we offer more than just a quick oil swap. Our team is dedicated to giving you a higher standard of service, especially when it comes to diesel maintenance.
- Specializing in Diesel: Diesel engines require specialized knowledge and care. Whether you drive a Ford Super Duty, Cummins-powered Ram, or Duramax Chevy, we use the right synthetic or blend oil, OEM-grade filters, and proven techniques to keep your engine performing at its best.
- Advanced Equipment: Our shop is equipped with top-tier tools like the Hunter Hawkeye Elite alignment system, Road Force balancing, and touchless tire machines that handle oversized and carbon fiber wheels with ease.
- Transparency You Can Trust: We offer Digital Vehicle Inspections (DVI) with photos or video, so you’ll know exactly what’s going on with your vehicle, no surprises, no pressure.
- Warranty Confidence: We stand behind every service with a 24-month/24,000-mile warranty, and we will honor the specifics of your manufacturer’s warranty to help protect your investment long-term.
- Convenience Matters: With extended weekday hours, a cozy waiting lounge, a kids’ area, free WiFi, and text-to-pay options, we make your visit easy and stress-free.
From hardworking diesel trucks to daily drivers, FloState delivers oil change services with integrity, expertise, and a commitment to long-term engine health.
Don't Let Bad Oil Break Your Engine, Act Before It's Too Late
Noticing a burning smell, ticking noise, or drop in performance? These are signs your oil may be doing more harm than good. Don’t wait, protect your engine before small issues turn into major repairs.
At FloState Auto Diesel Repair, we provide expert oil change services for diesel, hybrid, and gas vehicles. Our ASE-certified technicians deliver honest, high-quality service backed by a 24-month/24,000-mile warranty.
Visit us at 1396 Hamlin Avenue, St. Cloud, FL 34771
Call us at (407) 498-4204 or schedule your appointment online
Proudly serving St. Cloud, Lake Nona, and surrounding areas including 34771, 34772, and 32832.