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What Adding Boost Can Do To Your Engine Oil

Remember that 80’s commercial about your brain on drugs? Here’s a simile with respect to why using a higher viscosity motor oil or simply changing your engine oil more often might be necessary in your turbocharged car.

In a recent The Oil Geek YouTube channel episode, the host of the show does an impressive demonstration he referred to as, “This is your oil, this is your oil on boost” after performing oil analysis looking at how motor oil can be affected comparing an engine that is naturally aspirated with one when it is boosted with a turbocharged system. While this pertains primarily to racecar designed engines, it is informative toward what could be going on under the hood of your turbocharged car.

'80s Anti-Drug Commercial - Your Brain On Drugs

What is Boost?

Basically boost is what you want in today’s smaller engine cars to ensure that while in traffic you can get the pickup and go you need occasionally to either pass another vehicle like a long hauler or reach escape velocity when you find yourself in a merging lane and that merging vehicle is approaching you dangerously close because he or she will not back off or respect the solid white line.

Boost is achieved by physically forcing more air into a car’s engine to cause the fuel in the cylinders to burn more effectively and efficiently, which results in more power i.e., boost to your engine.

Before turbocharging in today’s cars, engines were naturally aspirated meaning that the air entering the engine is under the same pressure as your atmospheric pressure you and your car breathe in.

At some point when engineers were experimenting with improving the air intake of cars, a supercharger system was tried.

What is a Supercharger?

A supercharger is a vehicle fitted with an air compressor that actively pushes more air (thus more oxygen) into the intake manifold and then on into the engine cylinders.

The supercharger was powered by a belt from the engine crankshaft, which spun components within the supercharger creating a vacuum that pulled and then squeezed more air (thus more oxygen) into the engine than was possible in a naturally aspirated engine.

However, because a supercharger is powered by a belt from the engine crankshaft, a supercharger steals some horsepower from the engine.

A better solution was the development of turbo chargers that would not steal horsepower from the engine, by using exhaust gases to recirculate from the engine into the turbine of a turbocharger feeding the intake manifold. Coupled with a direct fuel injection system, this resulted in more power and better fuel efficiency.

Examples of such are today’s cars that include Ford’s line of vehicles with the 4-cylinder, 1.0 liter to 3.5-liter EcoBoost engines that are much lighter than earlier V8 engines, but produce comparable power with a turbo system installed.

Related article: Ford EcoBoost Engine Oil Breakdown Problem

What Happens to Oil When Boost is Applied

In the demonstration from The Oil Geek YouTube channel episode, what the host shows in a racecar style engine designed to receive more boost than what is achieved in a commercial stock vehicle today, is that via the combination of increased air and increased fuel, the resulting effect is lowering of the motor oil viscosity and prematurely breaking the oil down, which results in increased wear and tear on the engine.

Related article: The Truth About Turbo Engine Reliability from This Car Shopping Expert

The Value of This Video

The value of this video is that it is instructive in how differing oil viscosities under a range of differing running conditions can and will affect motor oil when an engine (whether a racecar type or your family car) is pushed to its limits. The data charts shown will also help you interpret and understand what is significant should you ever decide to have a sample of your engine oil analyzed.

Oh yes, and then there’s watching the dyno run. I can never get enough of that.

Related article: Blown Turbo at Only 60,000 Miles on This Chevy. What Happened?

What Boost Did to Our 5W-30 Motor Oil...


The Takeaway Message for Car Owners (in case you did not watch the video)

The takeaway message of the video demonstration is that as you increase boost in an engine using a turbocharger or modifying an existing turbocharger for even more boost, you are increasing the amount of fuel that is needed in the engine. However, not all of the added fuel is being burned; Some of it actually makes its way into your engine oil. Doing so results in thinning your engine’s motor oil which means lower viscosity and premature wear and tear on your engine. The end result is that to protect your engine with boost, you may want to consider changing your oil more often than every 5,000 miles to something closer to every 3,000 miles in a turbocharged car.

In other words as pointed out by one comment following the video: Boost = more fuel and air = more burn from the mixture = more pressure = more blow-by = more dilution.

Just as a reminder: “Blow-by” is a term commonly used to explain the phenomenon of fuel or oil escaping past the piston rings into the crankcase or the combustion chamber respectively due to increased pressure and/or worn piston rings. In the case of boost, the increased pressure is causing fuel to contaminate the engine oil.

But Wait. There’s More…

One other important takeaway message is that it is not just about the decrease in viscosity in motor oil while running a boosted engine, but also about how the engine is ran.

The host showed a surprising finding that if the engine is allowed to idle between multiple power runs on the dyno, the oil is fine aside from the fuel-diluting. However, if the engine is allowed to cool between runs, water condensation occurs in the oil, which further adds to motor oil degradation.

What Does This Mean to My Turbocharged Car?

Bear in mind that as mentioned earlier, the tests were performed on a racecar-designed engine which is likely to have greater bearing and piston and ring clearances due to thermal expansion expected from an engine that is ran harder i.e., hotter, than a non-racecar engine.

In a normal boosted commercial car this may or may not apply depending on the engine’s design. However, if you take an existing model designed with turbo and desire to modify it to give the engine an even more added boost, then you may want to take the test results into consideration.

In any case, this was a very interesting demonstration by The Oil Geek YouTube channel host that shows how changes made to an engine can and does change its motor oil requirements; AND, that when it comes to deciding on what type of oil is used and how often it should be changed, that environmental effects like how hard you run your engine and under what conditions, is just as important to the life of your engine.

Timothy Boyer is an automotive reporter based in Cincinnati. Experienced with early car restorations, he regularly restores older vehicles with engine modifications for improved performance. Follow Tim on Twitter at @TimBoyerWrites  and Facebook for daily news and topics related to new and used cars and trucks.

COMING UP NEXT: Car Dealers Caught Overcharging Buyers

Image source: Deposit Photos