Every week Ask AutoGuide provides iron-clad vehicle-shopping advice to distressed, confused or otherwise bewildered consumers. Whether they’re in the market for a family-friendly crossover or something that’s good in winter weather, the Oracles of all things automotive have been there to lend some helping hands. But this week they’re taking a slightly different approach.
Aside from vehicle-shopping advice AutoGuide’s in-house experts regularly receive e-mails asking other questions. Recently Debbie sent in a message about oil. She wants advice on what kind of lubricant to use in her car.
Debbie drives a 2011 Nissan Sentra that’s rolled some 49,000 miles, quite a distance in just two years. That implies a lot of highway driving, which is generally pretty easy on vehicles. Unfortunately that’s not the case because she’s a private investigator. This means her car idles extensively in all kinds of weather conditions in order to keep the climate control system on and frostbite or heat stroke at bay. This sort of usage scenario is very hard on oil. So, what kind should she be using? As Debbie’s champion the Oracles reached out to an expert in the field for answers.
“That kind of operation is what we call severe” said Z. George Zhang, Ph.D. and CLS manager of Valvoline’s R&D Lab in Lexington, Kentucky. To counteract any damaging effects the good doctor said “No. 1 we want a premium product like synthetic or our MaxLife [oil].”
SEE ALSO: What is Motor Oil?
One of the major reasons extensive idling is bad for engines is that it leads to water buildup in the lubricant. H2O is present in the air and it’s a byproduct of combustion so it’s inevitable that some of it ends up in the crankcase.
With water accumulation Zhang said three things can happen. The first being rust. Engines contain a lot of bare metal surfaces and oil plays a major role in protecting them from corrosion.
“Second, water combines with additives” he said, which can result in the formation of milky-white sludge. This byproduct looks like dirty mayonnaise and among other things it, “Brings down some of your dispersants and detergents,” destroying the oil’s ability to protect the engine.
Lastly, Zhang said moisture can freeze in the cold weather, which is obviously not good.
One way to alleviate this water retention issue is to get the engine nice and hot. The optimum temperature for oil is anywhere from 160 to 200 degrees Centigrade (320 to 392 degrees Fahrenheit), a level it doesn’t necessarily reach while idling. Zhang said oil temperature and overall engine temperature are two different things.
Moisture boils away at just 100 degrees C (212 degrees F). In order to get an engine hot enough Zhang suggests taking the car out for a high-speed drive on the freeway for at least half an hour twice a month. This “[makes] sure the oil reaches the optimum temperature,” he said.
In addition to using quality oil and getting the engine hot from time to time Zhang said Debbie should “follow the owner’s manual.” He recommends going by the severe-duty service schedule, which specifies more frequent fluid changes. He also said extended drain intervals are strictly prohibited. Some refiners sell oils they claim last for tens of thousands of miles but Zhang said steer clear of these.
Arguably the best lubricant advice is simple. Zhang said, “You want to use a premium oil” because they have, “more chemistry to fight any possible moisture,” a big problem for vehicles that idle a lot, just like Debbie’s. This is also sound advice for other drivers that want to keep their cars running strong for years to come.