Cary's Garage: Oil Striction

Cary Hubbard
by Cary Hubbard
cary s garage oil striction

Recently I was talking to several people I know about maintenance and care for a couple of Powerstroke Diesel engines and was surprised that neither had heard of oil stiction and the effects it causes.


For this piece, I had the idea it would be a good idea to cover it briefly. I am not sure if this subject has been covered before, but if it has here is a refresher on the issue.

Over the years of doing mechanical work, I have always been curious that most people don’t understand the effects it has and truly how different the engine will run when it is not addressed.

The word stiction is the combination of static and friction. The best way to think about it is like cholesterol problems but for a diesel engine, and it “clogs” up the system, thus not allowing the proper flow. The problem occurs in any vehicle that uses HEUI-Type injectors (Hydraulic Electronic Unit Injector). This is mostly seen in 7.3- and 6.0-liter Powerstroke diesel engines on the road in the U.S., though I’m sure it happens in other applications. The Powerstrokes use an HPOP (High-Pressure Oil Pump) that gives the oil pressure to fire the fuel injectors. So, you can imagine when you have a friction problem on something that is so important to how the engine runs there will be noticeable effects.

Commonly I get asked how to make my truck run better, start easier, idle smoother, and/or get better fuel mileage; and my question in return is if they are running an oil modifier in the engine. Now don’t be mistaken: This won’t be the magic cure-all for it, it obviously needs to have its systems working properly. Yes, it will have a hard time starting if the glow plugs aren’t working. Yes, it will run poorly if your fuel filter is plugged up or the injectors or plumb wore out. But say everything is in good working order and you are still wondering if there is more to give, yes there is.

The effects of oil stiction will cause hard starts, poor idle, and poor throttle response. All these things are reliant on the oil in the engine, so having friction issues will obviously have quite the effect.

Doing regular interval oil changes with a quality oil is the best place to start, and with every oil change, you need to add an oil friction modifier to the system. I won’t go into specific brands, but for you doing a simple search on oil friction modifiers and you can make a decision on which is best for you.

The whole idea might sound a bit like “snake oil”, but I have experienced the difference several times either with my own truck or helping friends. I had an OBS F250 Powerstroke that has had its fair share of issues, and after I went through all the normal items it still never seemed to be on point in terms of how it should run. I ran an oil friction modifier in that engine and was honestly amazed at how it smoothed out, had a much faster throttle response, would start easier in the cold, and even started to see improved fuel mileage on several trips I took with it.

Best of luck out there and if you are unfamiliar with this issue and start to run the friction modifier in your engine and notice a difference. Let me know, I would be interested to hear your response to it.

Please send me an email at Carysgarage@gmail.com and I will answer your questions here! Happy New Year!!

[Image: BLKstudio/Shutterstock.com]

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  • Pig_Iron Pig_Iron on Jan 02, 2023

    Stiction is also a concern with motorcycle forks, amongst other applications 🏍

  • Sayahh Sayahh on Jan 03, 2023

    I haven't heard of this word before, but is it stiction or striction?


    "Cary's Garage: Oil Striction"

    • Bullnuke Bullnuke on Jan 03, 2023


      Stiction is the proper term. Two moving surfaces tending to stick together when attempting to commence moving them independent of each other is called stiction.


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  • ToolGuy Weren't some of the most powerful engines in the M4 Sherman air-cooled? (And supercharged.)
  • ToolGuy "I installed oil temp and cylinder head temp gauges on various vehicles I was driving, so I could monitor how the engine was doing. I switched from my normal 20W50 and dropped to 15W40 oil and put down thousands of miles. Within that time, I saw a noticeable decrease in oil temps and even cylinder head temps while driving in different situations."ToolGuy has great admiration for your use of the scientific method in conducting original research.
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