0W engine oils improve fuel economy – but they aren’t good for diesel pickup engines
By Larry Walton
When “zero-weight” engine oils came on the scene several years ago, the majority of those who use their pickups for work or in a fleet application were a little skeptical such oil had any place other than in trucks that operated in the below-zero temps of the far north.
Such skepticism is warranted: 0W oils are better than the more conventional 5W and 10W oils in sub-zero conditions because they provide better turbo lubrication on cold starts, easier engine starts and better fuel economy than their heavier-weight brethren.
But in the majority of cases 0W engine oils have yet to prove their worth in pickups.
All of the Big Three’s truck diesels are still required to run a minimum of 5W-40 in sub-zero temps or 15W-40 in warmer operating conditions.
The 0W synthetics were designed in large part because of auto manufacturers’ never ending search for better mileage and improving their CAFE (Corporate Average Fuel Economy) numbers.
That’s why 0W products such as Mobil 1 0W-20 Advanced Fuel Economy, GM dexos 1, Shell Rotella T6, Chevron Delo 400, Royal Purple, Amsoil and others are gaining the attention of fleet owners who are always on the lookout for fuel saving measures.
Back to oil basics, the number in front of the “W” in a multi-grade relates to the oil’s viscosity when cold (think winter-grade) as set by The Society of Automotive Engineers (SAE), while the number after the dash refers to the oil’s fluidity when hot.
In several cases, the engines and oils have been developed together as a collaborative effort between engine builders and oil company scientists.
“Developing motor oils with engine design teams is the ultimate goal of a scientist,” says Dr. Robert Sutherland, Pennzoil Technology Manager.
“Understanding the intricacies of an engine through conversations with engineers, allows us to formulate products that are optimized for the engine systems, resulting in increased protection and performance.”
According to Bob Mainwaring, Technology Manager: Industry Liaison and OEMs with Shell, “There is significant value in OEMs, fuel and lube companies collaborating with each other.
“Collaboration allows the design of hardware and fluids to be carried out synergistically – hardware [vehicle drivetrains] being matched to fluids and fluids being matched to hardware – all in an effort to cut emissions and improve mpg.”
So the OEM engine builders are aware of the fuel saving, 0W oils available.
0W OILS PLACE
One of those quick to adopt to the new 0W engine oils is GM.
GM’s 2014 Silverado and Sierra 1500s with 5.3L and 6.2L gas V8s come from the factory with ACDelco dexos1 0W-20, which is “good for all temperature ranges,” according to GM Powertrain’s Tom Read.
“However, GM does not recommend 0W oils be used in the Duramax; the Duramax should run 15W-40 and when temps are below zero, a 5W-40 can be used.” Says Read.
Ford and Ram gas engines still adhere to the use of 5W-30 engine oil and their diesels follow the 15W-40 line. Ford’s Super Duty owner’s manual says this:
“Engine oils with improved fuel economy properties (energy conserving) are currently available. If you use an energy-conserving oil, be sure it meets all the recommended Ford Specification, API service categories, and SAE viscosity grades listed in the Lubricant and Maintenance Materials Specifications chart.”
In other words, if you are thinking about changing the weight of oil used in your pickup(s), stay within the guidelines listed in the owner’s manual.
A zero-weight synthetic engine oil may deliver slight gains in fuel savings, but the number one job of engine oil is to protect the engine.
It does this best with the type and weight of oil the vehicle manufacturer has proven works for the climate and conditions in which your trucks are used.