Today’s vehicles are more efficient than we’ve ever seen. They are so efficient that most engines idling in an enclosed area for an extended time only produce enough deadly carbon monoxide to make you sick and give you a headache! Thanks to CNC machining, computer technology, and engineers steadily pushing the parameters of performance, efficiency, and comfort, we have reliable powertrains that allow us to cruise US highways at 65 mph (or more) while enjoying 25 to 50 miles per gallon fuel economy. While this is amazing, it comes with a price.
Engine technology has fundamentally remained the same, with add-on management systems being the most notable changes. However, what isn’t advertised are the internal changes made to allow the engine to be more efficient. Specifically, internal components were changed to allow the engine to operate with less friction. Unfortunately, the changes led to higher oil consumption, creating other related concerns. This article will point out some problems that bring newer vehicles to your transmission repair shop that have everything to do with their engine oil!
CHECK THE OIL LEVEL FIRST!
Since most drivers don’t check their engine oil level, they surely can’t recognize poor engine oil conditions. Manufacturers add insult to injury in this area by extending the recommended oil change intervals to 5,000 and 10,000 miles. The maintenance reminder lights are programmed to reinforce this too. So, drivers who pay attention to lights that come on in the dash and dutifully make their way to their favorite service center to stay on top of issues may be doing the bare minimum to keep their vehicle alive!
Most late model engines use piston seal rings that are much thinner and lighter. As a result, the engine creates less friction; however, they don’t seal as well as the previous generation rings used on earlier engines. Since the job of piston rings in an engine is to seal the combustion chamber for compression, keep the exhaust gases out of the crankcase, and keep the oil out of the combustion chamber, the reduced dimensions and weight allow oil and combustion to intermingle more. Therefore, it is common for most late model engines to consume one quart of oil or more before needing an oil change. As a result, some manufacturers inform their customers in the vehicle owner’s manual to check the engine oil level at least once a month and add oil as needed.
THE RELATED PROBLEMS
Since we are no longer just diagnosing transmissions but rather powertrain systems, it is imperative that we pay attention to what is happening on the other side of the flywheel. A poorly maintained engine can create numerous driveability issues that are difficult to track down. Many of these issues are blamed on the transmission. Here, we will look only at items related to engine oil concerns.
In all cases of possible engine oil-related concerns, we must verify the following areas in detail and certainty:
- Engine oil level
- Engine oil condition
- Correct engine oil viscosity
- Engine oil filter, hoses, and auxiliary cooler condition
Since most manufacturers have a low oil pressure warning system and/ or safety operating strategy, you don’t need to use a pressure gauge. If any of these items are in question, correct them before further diagnosing issues.
Most issues you will run into related to engine oil concerns will fall under driveability, shift quality, and/or shift scheduling. Issues experienced are as follows, but not limited to:
- Harsh shifting
- Limited power
- Limited shift range (no high gear, no TCC command, etc.)
- TCC related (bumps, TCC chatter, etc.)
Note that these conditions may or may not be accompanied by DTCs. Therefore, always scan all modules and address trouble codes first. Now, let’s look at some common related systems that are affected.
Variable cam timing became more prominent in the 2000s among numerous other manufacturers. By retarding and advancing cam timing, a smaller displacement engine has a broader torque and horsepower operating range, making it feel like a larger displacement engine while saving fuel. The majority of the OE manufacturers use engine oil pressure for the control components that operate the system. Sludge, debris, and low oil level cause the cam control system to malfunction, creating misfires, low power, and/or fail-safe engine management to be engaged.
Control solenoids are often the components that fail in this case. For example, GM’s 1.5L, 1.8L, and 2.4L engines use Variable Valve Timing (VVT) Solenoids to direct oil to change cam timing based on computer command (figure 1). Unfortunately, it is common to pull this solenoid on a poorly maintained engine and find the screens severely restricted. A restricted solenoid can cause vibrations, surges, and shutter complaints that mimic torque converter clutch-related issues.
Variable intake and exhaust control like the Eaton system used in GM’s 2014 and later 2.5L (RPO LCV and LKW) applications may exhibit shudder and surge complaints when the system malfunctions. A control solenoid uses engine oil pressure to control intake lifters for low lift during cruising and low demand conditions and high lift (default) for high demand and warmup (figure 2). Again, compromised oil conditions and/or volume directly affect the operation of this system.
Cylinder kill strategy is becoming a more common fuel-saving strategy in larger displacement engines. Manufacturers can increase fuel mileage by deactivating cylinders not needed to maintain vehicle movement relative to demand. GM uses their Displacement On Demand (DOD), Active Fuel Management (AFM), and Dynamic Fuel Management (DFM) in most of their V6 and V8 gas applications. RAM uses the Multi-Displacement System (MDS) on their V6 and V8 gas engines. This strategy is effective; however, it comes with a long-term price. Cylinders operated without fuel or compression can draw oil into the combustion side of the rings easier, causing higher oil consumption. Also, the deactivation components can stick and malfunction, causing misfires, surges, and vibrations during normal operation (figure 3).
Mopar’s 2.4L engine, which is found in several compact and midsize applications, has its unique problem. In some instances, the engine oil consumption is excessive by their standards. A consumption rate of one quart per 2,000 miles is considered normal. Mopar issued a customer satisfaction campaign notice W20 to address this concern with specific 2014 to 2019 Jeep, Chrysler, and Dodge applications (see factory reference material for your vehicle application). The problem that comes into play is the complaint associated with low oil on these applications; the engine dies! Of course, this is an intermittent issue when the oil gets low enough, and the vehicle accelerates or decelerates just right.
The problem is easily mistaken for a torque converter clutch applying, causing the engine to stall. Note that aggressive driving, defined by the OEM as consistent engine operation at 3K rpm and above, causes accelerated oil consumption with this engine.
So, with everything taken into consideration, how do you advise a customer so they can take good care of their vehicle? Since the old rule of thumb, changing your oil every three months or 3,000 miles, worked so well, this may be the best preventative advice to pass to your customers. After all, you can’t create a problem by changing your oil more frequently than recommended! Also, add a quick show-and-tell lesson upon delivering the vehicle to the customer on how to properly check and add engine oil, ensuring they know the proper weight to use for their vehicle. These few extra service steps may not only preserve the customer’s vehicle life but may prevent a comeback that has nothing to do with your transmission.
Diagnosing powertrain systems can be complex and challenging; however, starting with basic checks can sometimes open the window to a solution sooner than later. Never underestimate the power of basic maintenance, especially when diagnosing modern vehicles!
