The slippery business of choosing the right engine oil

OILS WELL

Curiosity brought me toward the open hood of a big Ford Super Duty whose owner was stretched up on his toes carefully wiping the last drops of fresh oil from around the engine’s oil filler neck. It was obvious he took great pride in keeping his truck and the trailer it was towing very well maintained.

After tossing the empty oil bottle in the trash, I noted it was a different viscosity than what the cap on the filler neck indicated. When I asked the owner why he used a 10W-40 instead of the 5W-30 listed on the oil filler cap, he felt it “gave a little better protection.”

Maybe in his mind, but that's not what the experts say.

“The biggest mistake vehicle owners make is using the wrong viscosity of oil, and that costs them both fuel economy and power,” says Pete Misangyi, Ford Supervisor of Fuel and Lubricants Engineering. “Using the wrong weight oil can reduce fuel economy 3- to 4-percent and have similar effect on power.”

But there’s a lot more to oil than the viscosity, and those who work on engines day in and day out know exactly what that means.

“Remember the old Fram commercial where the guy holds up the oil filter and says, ‘Pay me now, or pay me later,’” said Jerry Woodcock, service manger for Charlie Henderson Ford in Waveland, Mississippi, when asked about oil changes and preventive maintenance.

“Well, that’s exactly the case when it comes to servicing the engines on pickups and SUVs that see a lot of hard use like towing big boats and travel trailers.”

Woodcock says the $75 it costs to do a full oil service a Ford 7.3L or 6.0L diesel is far cheaper than the $7,000-$10,000 it costs for a complete rebuild—a job they see quite often.

He says if owner take the time and effort to have a gasoline engine’s oil and filter replaced every 3,500-5,000 miles it should provide years of service and run more than 150,000 miles without a thought of seeing the inside of a shop for a rebuild. Take similar care of a diesel and it may well see double that mileage before an overhaul becomes necessary.

However, try to stretch those oil changes out and you might as well start setting aside the monies for a rebuild or replacement in half that time.

But preventive maintenance is more than just “changing” the oil. It’s also very important to use the right oil for the right application.

“Selection of the proper engine oil for use in pickups is critical to engine longevity,” says Allan Perry, coordinator of Product Technical Services/Kendall Oil and 76 Lubricants. “Which oil is used should be based on the type of engine and operating conditions such as speed, loads, temperature and driving cycle.

“It should meet the recommended Society of Automotive Engineers (SAE) viscosity grade, American Petroleum Institute (API) and International Lubricant Standardization and Approval Committee (ILSAC) performance level specified in the owner’s manual.

These recommendations are based on the engine builder’s knowledge of what is best for that specific engine and application under different operating conditions.”

OIL'S HOUSEKEEPING DUTIES

Automotive oils are a concoction of “base” oils fortified with special “additives” designed to perform specific tasks. When these additives are mixed in with the base product, the lubricating oil you find on store shelves is created.

Everyone knows engine oil provides lubrication and a cushion between the moving parts. What many RVers don’t realize is that very same oil must perform some basic housekeeping chores, such as removing sludge deposits, neutralizing acids created after the combustion process, removing other combustion byproducts, and preventing corrosion from water and acids.

Oil is also a primary cooling source, transferring heat from the hottest areas of the engine so it can be dissipated in the oil pan and oil cooler. And all this time the oil has to protect itself from heat, oxidation and moisture contamination. It’s a tough task.

Some oils may look the same in packaging, but are much better performers between oil changes. A cheap oil may “meet” the basic requirements set forth by engine manufacturers, but a better quality oil will “exceed” those requirements.

“Commercial diesel engine oils and gasoline engine oils are fully formulated lubricants made with a carefully balanced combination of additives specifically tailored to the specific application,” says Kendall’s Perry. “They are designed for use as is without any further modification or additization.”

Commonly used additives include detergents, dispersants, antioxidants, antiwear agents, rust and corrosion inhibitors, friction modifiers, and antifoam agents.

“Collectively, these additives help to keep the engine clean, retard oil oxidation, protect against sludge and varnish deposits, and extend oil life,” Perry explains. “They also provide wear protection, rust and bearing corrosion protection, and resistance to foaming.”

GASOLINE OIL GRADES

That’s the reason there are special codes on every oil container that give consumers a pretty good idea of the quality of the oil.

Look closely (this might take a magnifying glass—honest!) at the back of any oil container and you’ll see the “grade” of the oil; the better the oil, the more letters and higher the numbers behind the letters found on the container labeling.

The basic almost all gasoline oils meet is the API “SL” standard.issued in July 2001. Better grades may have the ILSAC (starbust symbol) GF-3 code.

Oils with these designations on their labels meet 2001 OEM warranty requirements, according to Maurice E. Le Pera, owner of Le Pera and Associates, a leading petroleum consulting firm in Harrisonburg, Virginia. (Oils labeled with “API SJ” and “ILSAC GF-2” were for 1997 OEM warranty requirements.)

Oil labeled with “ILSAC GF-3/API SL” is the current industry standard for gasoline engine service and should perform excellent in your gasoline-powered RV.

Later this year the 2004 OEM warranty requirements will be raised and get a new rating: ILSAC GF-4.Oil with that label will replace ILSAC GF-3. Use an oil with the newer designation and your engine will be even better protected.

DIESEL OILS

Diesel oils are as different from gasoline-only oils as the engines themselves. That’s because oils designed for diesel use must contend with far dirtier conditions within the engine. So it’s very important to read the oil labels closely to make sure the one you’re choosing is designed for diesel use.

(You can use an some oils designed for diesel-use in a gasoline engine, but you can’t use an oil blended specifically for a gasoline engine in a diesel.)

“Diesel engine oils require higher levels of dispersancy and alkaline reserve (TBN) than gasoline engine oils in order to handle soot and higher levels of corrosive acids,” says Perry.

Perry says most engine builders of today's high-performance diesel engines recommend an engine oil meeting at least API “CI-4” performance requirements.

Diesel oil labeled wit the API CI-4 grade is the most current industry standard for heavy-duty diesel engine oils, and are designed to meet the lubrication requirements of many newer, low-emission diesel engines as well as older generation diesel engines.

There is a caveat; some engine builders, such as Cummins, Navistar, Caterpillar, and Detroit Diesel may have additional lubrication requirements specific to their engines that must also be met.

That is why such oils as Shell RotellaT (API CI-4, CH-4,CG-4, SJ/SL) and Castrol RX (API CI-4, CH-4, CG-4, CF-4, CF/SL) have notations on their labels referencing they meet or exceed the use requirements of those manufacturer’s diesel engines.

Those extra additives that provide the added engine protection are why such oils cost more. More than once the experts we interviewed all said the same thing: When it comes to engine oils, you really do get what you pay for.

That is why it can’t be stressed enough to read your motorhome’s owner’s manual very carefully to find the minimum oil grade requirements—or risk voiding the engine warranty should any problems arise.--BWS