New engine technology poses many challenges. Smaller displacement engines producing more horsepower with lower emission output, while achieving better fuel economy, come with their own set of challenges once the vehicle has been put into service. During the initial break-in of an engine, it is not uncommon for the engine to consume some oil. Once the rings seat to the cylinders, oil usage usually diminishes.
The problem comes when the engine initially does not consume any oil, but starts consuming oil when the mileage approaches 30,000-40,000 miles. When this occurs, the lube shop often gets blamed. The vehicle manufacturers list expected oil consumption rates based on mileage and operating conditions.
Review these expectations when dealing with a customer concerned about oil consumption. You may be shocked to learn that some consumption rates, based on driving conditions and mileage, may reach one quart in 500-750 miles and should be considered normal. Let’s consider some cases of excessive oil consumption and the vehicle manufacturer’s recommendations:
Software Update
Honda TSB 11-033 identifies 2008–2011 applications with specific VIN codes that may encounter excessive oil consumption in addition to an illuminated malfunction indicator lamp (MIL) and trouble codes P3400 and/or P3497 stored in memory. These codes set when the oil level drops to a level where the line pressure can no longer support Variable Cylinder Management (VCM) operation. During light throttle conditions on flat roads at cruising speeds, the VCM function may repeatedly switch on and off. The frequent switching can contribute to increased oil consumption. Honda has a software update that improves the VCM timing during the mentioned throttle conditions, reducing oil consumption.
Honda V-6 with Variable Cylinder Management
Honda announced a powertrain warranty extension of eight years with unlimited mileage from the original date of purchase. Honda stated the piston rings on certain cylinders may rotate, allowing the ring gaps to align, creating excessive blow-by and spark plug fouling. The MIL lamp may be illuminated with codes PO301 through PO304 stored in memory. Honda TSB 13-078 covers the necessary diagnostic and repair procedures, which require cleaning the pistons and replacing the rings on the affected cylinders. Verification of eligibility is based on VIN status. Vehicles affected include 2008-2012 Accord, 2008-2013 Odyssey, 2009-2013 Pilot, 2010-2011 Accord Crosstour and 2012 Crosstour, equipped with the V-6 engine with VCM.
Toyota 2.4L (2AZ-FE) Excessive Oil Consumption
Toyota has acknowledged reports of excessive oil consumption on the following vehicles equipped with the 2.4L (2AZ-FE) engine: 2007-2009 Camry, 2007-2011 Camry Hybrid, 2007-2008 Solara, 2009 Corolla, 2009 Matrix and 2006-2008 Rav4.
The Toyota dealer will perform an excessive oil consumption test to determine if the vehicle is eligible for repairs under a limited warranty campaign.
If excessive oil consumption is determined, the engine will receive redesigned piston and ring assemblies. The primary coverage offers warranty enhancement until October 31, 2016, regardless of mileage. The secondary coverage is applicable for 10 years from the date of first use or 150,000 miles, whichever occurs first. This is a warranty enhancement, not a recall.
GM’s Excessive Oil Consumption
Excessive oil consumption may be encountered on GM applications equipped with Active Fuel Management (AFM), once the vehicles log 30,000-40,000 miles, and especially vehicles operated at high engine speeds for an extended period of time. Vehicles affected include year models 2007-2012, and they are illustrated in Mighty Tech Tip #175 Excessive Oil Consumption. The Tech Tip expands on the information provided.
The problem stems from oil spray from the AFM pressure relief valve located in the crankcase. The oil spray causes deposits to form on the piston ring grooves, causing the rings to stick. New pistons and rings may be required to resolve the excessive oil consumption condition. A new deflector oil shield (GM P/N 12639759) should be installed on the AFM pressure relief valve.
LARRY HAMMER is an automotive troubleshooter who oversees Mighty's Technical Support Services in Jackson, Tennessee. Hammer has been writing technical articles since 1982. He may be reached at: [email protected]
