Fuel Economy vs. Drain Intervals


ISTANBUL – Automakers will need to make significant improvements in fuel economy in coming years. Lubricants can make a small but valuable contribution, a Lubrizol official told an industry conference here last week.

Engine oils could boost average fuel economy by approximately 1 percent, according to Mike McCabe, regional business manager for engine oils at Lubrizol, who spoke Friday at the annual meeting of the Independent Union of the European Lubricant Industry (UEIL). He added, though, that oil drain intervals may need to be shortened for the industry to meet its goals.

Fuel economy is not a new challenge for the lubricants industry. Helping vehicles consume less gasoline and diesel has been a priority the past decade, along with protecting engines from wear, lengthening drain intervals and avoiding damage to emissions control systems. Engine oil standards in Europe and the United States now include fuel economy performance requirements.

But fuel economy demands will apparently increase in coming years as pressure mounts to curb generation of greenhouse gases. For automobiles, the focus on pollution restrictions will shift from nitrous oxides and soot to carbon dioxide. Governments will try to reduce CO2 emissions by requiring vehicles to go further per unit of fuel.

In Europe, average vehicular CO2 emissions fell from 186 grams per kilometer in 1995 to 158 g/km in 2007. But the European Union has set a goal of further reducing that average to 130 g/km by 2012. To help prod automakers, the region has proposed fines that would phase in over the following eight years. They would assess penalties of 5 per vehicle for the first gram over the limit, 15 for the second gram, 25 for the third and a whopping 95 per vehicle for every additional gram above the limit.

The potential liability for automakers is enormous, McCabe said. By 2015, if vehicles still emitted as much CO2 as they did in 2006, the industry would face penalties of more than 34 billion.

The incentive is there to improve emissions performance, McCabe said. And if you look at the improvements that have been made since 1995, we have quite a lot to do.

Faced with such penalties, every little contribution toward fuel economy becomes valuable. A 1 percent improvement from 2006 levels would reduce CO2 emissions by 1.5 g/km, McCabe said, saving the auto industry 2 billion per year in fines avoidance, or 143 per vehicle.

Even such small improvements wont be easy.

Delivering 1 percent more fuel economy on top of what we already do today is going to be quite a challenge, McCabe said.

He proceeded then to lay out how Lubrizol believes engine oils can contribute. One is by making oils thinner. A 5W-30 oil can provide as much as 2 percent to 3 percent better fuel economy than a 15W-40 RL 191 reference engine oil, based on results of the M111 Fuel Economy engine test, which is part of ACEA engine oil standards. A 0W-20 oil scores as much as 4 percent better than the reference oil.

Oil formulators can make a bit more contribution by using different friction modifiers. Lubrizol conducted tests showing a 0.4 percent gain in the fuel economy of a 5W-30 engine oil by adding 0.3 percent molybdenum dithiocarbamate (MoDTC4) as a friction modifier. It achieved the same level of improvement by instead using a standard organic friction modifier. But then it achieved a 1 percent improvement by substituting 0.5 percent of a new organic modifier.

The industry has already been shifting toward lower viscosity oils. In 2002, McCabe said, 15W and 20W products comprised nearly 40 percent of the passenger car engine oils consumed in Europe. By 2008 they comprised just 20 percent. During the same period 5W oils went from being approximately 18 percent of the market to 45 percent. Similar changes occurred for heavy duty diesel oils, where consumption fell for 15W and 20W oils and monogrades while rising for 10W and 5W products.

He argued that there is little choice but to continue on that path.

You can imagine that in the future well be moving toward 0W oils to get that elusive 1 percent of additional fuel economy, he said. Its really the only place we have to go. McCabe noted that Europe prefers 0W-30 over 0W-20.

He said industry will also need to take into account the fuel economy that vehicles achieve after oil is installed in an engine – not just the score that fresh oil achieves on an engine test. As oil ages in an engine, fuel economy decreases. Friction modifiers and other chemistries are depleted, the oil thickens due to oxidation and accumulation of soot.

Formulation can delay this decrease in performance, McCabe said, but only so much. To sustain fuel economy improvements, drain intervals may need to be shortened.

As fuel economy deteriorates over time, there comes a point when swapping an old oil for a new one becomes the best approach to better fuel economy, he said. It is hard to say what the optimum point is, as it varies by engine and cycle. But the overall trend is there: The longer a drain interval, the more fuel economy will deteriorate.

Related Topics

Market Topics