Not too long ago, I was talking to Scotti Lee, a recognized guru in the quick lube industry. He was sharing with me the sudden rash of oil-consumption complaints that were popping up in the industry. There have been several recent class-action lawsuits having to do with the problem.
The Volkswagen Group of America settled a lawsuit in May over excess oil consumption in some of their 2009 to 2011 model year Audis, according to the Los Angeles-based Margarian law firm, which specializes in Californias lemon law and dealer fraud suits.
A lawsuit was filed against Subaru in July 2014 alleging that certain models contain defective piston rings in the engine, causing excessive oil consumption. The suit is still active, according to legal firm Chimicles & Tikellis LLP, in Pennsylvania.
Chimicles & Tikellis LLP said it also filed a lawsuit in March 2014 alleging that certain Toyota and Scion vehicles contain defective piston rings that cause excessive oil consumption. This suit is also ongoing.
And there are others. Honda settled one back in 2013, and Mercedes-Benz, Volvo and BMW have had their share of complaints. So, whats going on and what does it mean to this industry?
The first thing to note is that oil consumption is universal and normal in engines. Every stroke of the piston wipes a very thin film off the liner wall and sweeps it into the combustion chamber. The amount is miniscule and is part of the normal operation of the engine.
Another point of exit for oil is down the valve guides, also into the combustion chamber. Again, not too much, but over time it does result in some oil consumption. Beyond that, there really isnt any place where oil is expected to be lost.
Most normal, well-maintained new engines today likely use less than half a quart of oil in 3,000 to 5,000 miles. Some use almost no oil. But as the engine miles grow, wear and oil consumption naturally go up.
For some engines, particularly those of the original equipment manufacturers involved in the class action suits, achieving high performance (high revs and high temperatures) means they will tend to consume more oil. These engines do consume at a greater rate, but the manufacturers know that and note it in dealer bulletins and sometimes in their owners manuals.
Higher than normal oil consumption has many causes and can create some issues that are difficult to control. Lets look at some of the major causes, starting with engine design.
When fuel economy first reared its head as a performance issue in the 1970s, engines were big and relatively inefficient. To their credit, the OEMs went to work to improve efficiency through some innovative designs. Most of the frictional loss in an engine is the result of ring-on-liner motion. Ive seen numbers from back in the 70s as great as 50 percent loss in efficiency due to a combination of pumping losses and friction.
For those who arent acquainted with pumping losses, thats the energy expended to admit the air-fuel mixture into the cylinder and expel burned gases through the exhaust system. This is probably the single biggest energy hog in the engine. Frictional losses are next in magnitude and are the enemy the OEMs have employed oil to fight.
Modern engines are, for the most part, smaller displacement, higher revving beasts than those models of 40 years ago. When fuel injection, turbocharging and computerized fuel and ignition management systems are thrown on top, it gets pretty difficult to control all of the oil parameters.
Certainly, we know that oil consumption rises with engine mileage. The engine becomes worn and clearances increase. That results in more oil being lost in combustion. Seals begin to weaken and oil is lost that way, as well.
Using a quart of oil every 1,000 to 1,500 miles is no surprise for a high-mileage engine – some would call it acceptable – but by the time it reaches a quart or more in 500 miles, thats too much. Blue smoke in the tailpipe exhaust is a classic sign that an engine is burning too much oil. An engine that burns oil will probably foul the spark plugs, causing combustion problems as well as trouble with the emissions system.
What mechanical issues could cause high oil consumption to occur? I got in touch with some of my OEM contacts for their viewpoint. They pointed out that crankcase ventilation is a possible culprit. Remember that the PCV valve takes vapors formed in the crankcase, which are made up of blow-by gases from combustion as well as any volatile materials from the oil, and recirculates them to the intake manifold.
Ring problems, such as poor seating, also can occur. One possibility is taking low-tension rings too far when trying to lessen ring-liner friction for better fuel economy. This is a strategy that has been employed by the OEMs – but mismanaged, it could sacrifice sealing in the process.
There could also be issues with the engine hone. Cylinder liners are machined to create a cross-hatch pattern ensuring oil will cling. According to some reports, oil burning can occur if the cylinders in a newly built or rebuilt engine are not honed properly (too rough, too smooth, wrong crosshatch), or if the piston rings never fully seat. Automakers plateau hone the cylinders so the rings will seat quickly. Plateau honing shaves the sharp peaks off the scratches in the cylinder wall after the initial honing so the finish will be similar to a broken-in cylinder. If the honing process is not done correctly, the rings may never seat.
Turbocharging, which appears now on more automobile engines than ever, may also carry the seed of higher oil consumption. Forcing more air into the combustion process results in more power output, but also raises the temperature of the engine oil since that oil cools the turbocharger bearings. If the oil is hotter, it stands to reason that more will be lost due to volatility. In fact, the smaller engines now in service tend to operate at higher temperatures overall, so volatility is definitely an issue, even without turbos.
One of the most rigorous test beds for engine development is the automobile racing circuit. The designs we see now are derived in some part from those power plants run in Formula 1 and open-wheel, IndyCar racing. But there are some significant differences. The puzzle of how engine design affects oils led me to seek out people with racing history, to share their insights into what goes on with a racing engine that may or may not translate to the street-legal version.
I turned to a former colleague of mine, Ed Gellner, who spent a lot of time with Sports Car Club of America racing and was involved in putting together some early racing oils.
Ed tells me that IndyCar engines from the 80s were all dry sumped. He describes these oiling systems as follows: They use scraper rails with maybe 50-thousandths [inch] clearance to remove excess oil from the crank and rods. Then they use vacuum pumps to extract as much oil as possible from the engine and send it to an external oil tank for air removal and some cooling… These cars had an oil tank capacity of about eight gallons. [Pit crews] could not add oil during the race and the tanks are far from full at the end of 500 miles.
Ed guesses that these engines consumed three to four gallons over the span of each race. As for oil formulations, he notes that they all use special formulations with lots of extra friction modifiers and very thin viscosities, like SAE 0W-20 or even less.
Now we come to the crux of the matter from an oil marketer point of view. Currently, many North American OEMs factory-fill their light duty vehicles primarily with SAE 0W-20. They do it in order to capture as much fuel economy from the oil as possible.
Theres reason to be concerned about both the high temperature, high shear viscosity and the volatility of these oils. In order to get to SAE 20 or 16 (or SAE 8, as Honda wants), pretty low viscosity base oils are required. And with low viscosity comes higher levels of volatility. Remember that PCV valve and the crankcase gases it recirculates? Thats where the volatile light ends of the base oil go – out the exhaust pipe.
Another problem with lower viscosity oils is that more can get past rings and valve guides to be burned in combustion and lost. There is also concern in some quarters that wear will increase, shortening engine life.
For oil marketers, this presents an opportunity to educate vehicle owners about how much oil consumption is normal and how much is not. The first thing to impress upon drivers is their responsibility to perform regular oil checks. Of course, they will know to check their oil if they get a low oil light on the dashboard panel, but more regular checks will allow them to perceive any oil loss. A general rule of thumb is to check it at every fuel station fill-up.
Drivers need to be educated that if the oil has dropped a quart after 500 to 1,000 miles, they should look around the vehicle to check for leaking oil, often a problem for older engines. If there is no visible oil leak, drivers should check with their car dealers service manager to see if there are any bulletins out about excessive oil consumption.
Industry consultant Steve Swedberg has over 40 years experience in lubricants, most notably with Pennzoil and Chevron Oronite. He is a longtime member of the American Chemical Society and SAE International, where he was chairman of Technical Committee 1 on automotive engine oils. He can be reached at steveswedberg@cox.net.