Diesel Smoking

Reading Smoke, What Your Exhaust’s Smoke Means

We’ve all seen (or have caused); thick, black smoke come from the exhaust of a diesel. It’s some guy’s favorite part of owning a diesel in fact. Let’s talk about the different colors of exhaust smoke, their causes and solutions.

Blue or Gray. Newer, low mileage truck owners can skip this paragraph, but many of us like to have a worn out beater truck laying around, or maybe your teenager bought their first car from a not-so-honest guy. Blue usually means one thing: you are burning oil. You might notice a burnt oil smell while stepping on the accelerator, or maybe see blue/gray smoke leave your exhaust on startup or heavy acceleration, these are some of the tell tale signs that you are burning oil. Do not rely on the oil light to remind yourself to add oil as for most cars this light simply means “shut the engine off immediately”. Common issues include piston rings, valve seals, PCV valves, injector o-rings, turbo seals or the turbo itself; depending on the vehicle.

Besides jumping into an engine rebuild, many owners try to narrow the cause down by starting at the lowest cost and working upwards. Stiction Eliminator is a smart place to start. It helps remove the built up coked and varnished oil and soot, prevents future coking, helping the rings and seals do their job, which in turn restores compression. The cleaning of the turbo, camshaft and other internals that oil comes in contact with reduces friction in the engine, helping to lower engine operating temperatures and making the engine run more efficiently and smoother. Stiction Eliminator belongs first on the list due to its money back guarantee and ease of installation. Next, many auto parts stores offer compression test units for rent, and you receive your money back when you return the tool. It’s a straight forward test for the backyard mechanic, and can help show the condition of your engine. PCV valves are usually the next cheapest, these can go bad and suck oil into the intake, depending on the vehicle. Consult your mechanic if unsure on your next step, many manufacturers have an acceptable amount of oil that might be burnt during normal operation as the vehicle ages.

White. This is usually the last color of smoke you want to see, particularly on gas cars. If the smoke is thin, and goes away relatively quickly, than it is merely condensation. However, thicker, longer lasting smoke is a much larger headache. Your engine is more than likely burning coolant. This can be the result of a blown head gasket, damaged cylinder head, or cracked engine block – none of these are easy on the wallet. Diesels can also put out white smoke when fuel passes completely through the engine and reaches the exhaust without having been burned. This might be caused from the engine being too cool to burn the fuel, low compression in cylinder(s), fuel injection timing, defective fuel injector, burnt out glow plugs, clogged air filter or poor quality fuel. Diesel Extreme is the go to solution for this color smoke since it attacks many of these issues. By improving the fuel’s cetane, fuel can ignite properly at a more desirable temperature once it enters the combustion chamber. Diesel Extreme contains powerful detergents and dispersants to removes water, bacteria and break down sludge, completely cleaning your entire fuel system, from the tank to the injectors. Another fix might include adding an automatic pre-heater, or unfortunately the entire replacement of your engine depending on the issue.

Black. Or as many people call it, “rolling coal”. People throw tuners, modules, or some kind of smoke switch, onto their diesel to make the truck add more fuel than necessary to create black smoke, as well as install larger injectors. But for those who don’t intend to smoke out everyone behind them, there’s quite a few things to check. A little black smoke is normal on a properly functioning diesel, but keep an eye on the amount of smoke at different RPMs and loads so that you will be able to tell if something is amiss. Incorrect timing or air/fuel ratio, dirty injectors or common rail injectors staying open for too long (too much fuel), a worn turbocharger, dirty intake manifold or clogged air cleaner, low cylinder compression, poor quality fuel, or excessive carbon built up in combustion chamber can all be culprits.

Stiction Eliminator is a great place to start when trying to get rid of black smoke. It will make sure the turbo internals, camshaft, and HEUI injectors are cleaned and lubricated. Stiction Eliminator helps restore compression to ensure that the combustion chamber is in optimum performance. For other situations a dose of Diesel Extreme might be what you need to clean out those injectors coked with burnt fuel and get them firing like new. Replacing your air filter, checking the intake manifold out, or fiddling with your aftermarket tuner might be the answer. If you are not sure what you are doing when adjusting your air/fuel ratio, don’t be afraid to ask a professional. Running rich (too much fuel) is always better than running lean (not enough fuel). A lean air/fuel ratio can damage an engine in a short amount of time.

14 thoughts on “Reading Smoke, What Your Exhaust’s Smoke Means”

  • My truck blows a haze that I can only see at night when someone is behind me when I’m getting up to speed or easing into it around town. During the day I see nothing but a bit of black smoke puff out the pipe until the turbo kicks in. What could cause this or what should I look at. Truck sound good runs strong it’s a 6.4 with 303k on the odometer deleted dpf/egr cooler, egr turned off.

    • Hi Cody! It could be a number of things, but if the truck is running fine I would start with an oil analysis to test for an intermittent coolant leak and fuel dilution. Thanks!

  • My diesel x5 is blowing white smoke continuously out of the tail pipe. I am also losing oil but there is no visible leak. Any suggestions

    • Hi Alex, we definitely recommend a tank or 2 of Diesel Extreme fuel additive for the white smoke, and a fresh oil change with Stiction Eliminator. After that, try FR3 Friction Reducer oil additive to further reduce burning/leaking oil…thanks!

    • I put too much oil in the engine and the next day ihad blue smoke i changed the oil but still comes blue smoke i put five literrs in excess thank you jp

      • Hi John, it will smoke for a little while, but will eventually dissipate if you have the correct amount in the crankcase. Thanks!

  • My 2001 DOES NOT SMOKE at all. I met a few of your representatives at the GATOR NATIONALS in 2014. “GREAT GUYS !” I’ve been using a triple combination of Lucas products. Both the ones you spoke of above and your TREMENDOUSLY GOOD fuel additive. My “3” 7.3 trucks all progressively began to run much better after about 500 to 800 miles of using your products. 187,000 miles on MY PERSONAL TRUCK and very close to 200,00 on the other two. “I DON’T KNOW WHAT YA ALL DO, BUT YA DO IT WELL.” Excellent products and I LOVE THE DISCOUNTS when you purchase in bulk. T.C. WOOD, THANKS

  • I really like how you noted that jumping to the conclusion that an engine rebuild is needed is generally not needed. Certainly, there are times when you’ll have to start from scratch, but this was a great collection of advice on how to avoid that. I’ve always relied on pros to take care of my vehicles, and I’ve heard similar advice from them, so thanks for the insight!

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