Chrysler recently donated a 2.4-liter MultiAir engine to my automotive department at Southern Maine Community College.  The engine is called MultiAir because the intake valves open to different positions for different times, providing the best air flow through the cylinders under varying operating conditions.

The engine is found in vehicles such as the Chrysler 200, Dodge Dart, and Jeep Cherokee.

An interesting feature of the MultiAir engine is that it is missing a camshaft. Usually there is a solid piece of metal transferring force between a timing chain and the valves, but this engine uses oil pressure to push the intake valves.

Oil pressure has been used for years to achieve variable valve operation, but it is remarkable to have fluid replace a solid part.  I recognize that we rely on brake fluid to transfer force to stop vehicles’ wheels, but operating an engine valve train with fluid is different because the oil has to get up to the top of the engine before it can do this job.

This leads me to question whether vehicle owners know how important it is to use the correct engine oil. We used to be concerned about oil simply preventing wear on the moving metal parts, but more and more, the oil has the additional purpose of pressurizing mechanical actuators, too.

As a fellow gearhead likes to say “Oil is like spandex. Just because it fits, doesn’t mean it’s right!”

If the wrong oil is installed, or if it’s too old, then it can’t flow to the actuators, and ultimately causes new symptoms besides plain old engine wear.   

For example a student’s newly purchased 2005 Subaru Forester recently showed up in the shop with the “check engine” light on.  He hooked up a scan tool and retrieved a P0011 code from the powertrain control module, indicating trouble with the camshaft position and timing.

After following the diagnostic flow chart for the code, we concluded that the solution was simply to replace the oil and filter.

While this was an easy fix for someone in the trade, it could be very inconvenient for a paying customer to go through this unnecessary hassle.

Oil quality, not just viscosity, is important.  Oil should be approved by a standards organization such as the American Petroleum Institute (API) or the International Lubricants Standardization and Approval Committee (ILSAC).  It’s even better to use oil that’s approved by the car manufacturer. GM, for instance, has its own, dexos brand oil.

Checking quick lube services in Portland, I found a wide selection of oil, but the choices may be confusing.

Beware of “high mileage” oil, which may invalidate the car’s warranty. A better choice is oil that meets specifications of manufacturers such as VW or GM, even though it will cost more than a standard oil change.

The manufacturer-specific oil may be expensive, but if it helps the variable valve train, then the engine runs more efficiently and fuel cost is saved.  If the correct oil saves a diagnostic fee for a check engine light, then it’s well worth the price.    

Ruth Morrison is an Automotive Technology Instructor and Department Chair at Southern Maine Community College.  She holds certification as an ASE Master Technician and Advanced Level Specialist and was a former Ford Senior Master Technician.  She graduated from the Ford ASSET Automotive Technology program at Central Maine Technical College and most recently earned her master’s in Adult Education from the University of Southern Maine.