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engine oil - Fact or Fiction?

Posted on April 20, 2016 at 9:40 AM

We all know that our cars need engine oil in order to operate smoothly. The role of engine oil is to keep the moving parts of the engine lubricated, to protect them against rust corrosion, and, with modern detergent oil additives,to keep them free of sludge and general engine gunk.


But most of us also know some things about engine oil that aren't actually true. For instance, isn't it always necessary to change your oil every 3,000 miles? And when the color of your oil starts becoming dark, doesn't that mean that it's about to fill your engine with harmful sludge?


Well, no. These ideas are myths. Let discuss them along with a few other engine oil "facts" that don't happen to be true. A little knowledge isn't necessarily a dangerous thing, but a little knowledge that doesn't happen to be true could quite possibly ruin your engine, or at least cost you a lot of unnecessary expense. 

Whats up with the different oil types? Oil changes its viscosity with temperature and the single viscosity rating only represents the flow of oil when it's warm. What if you need to start your car on a cold winter morning? The oil will flow more slowly, so the cold viscosity rating is important too. A multi-grade rating gives you both the hot and cold viscosities. For 10W-30 oil, the 30 is the same as the SAE 30 viscosity rating for warm oil, but the 10W is the viscosity rating for cold oil, according to a standardized rating system developed by the SAE for winter oil use. And that's what the "W" stands for: "winter."

Then theres that old rule of thumb, "change your oil every 3,000 miles". Keep in mind the key word - "old rule of thumb". It used to be that almost every auto manufacturer recommended that the oil in your engine be changed every 3,000 miles. Use oil past that interval and the engine would begin to fill with sludge, which would not only degrade performance but leave the moving parts at risk for damage.


That's no longer true. Modern detergent oils, improved oil viscosities and better auto engineering in general now allow cars to go about 7,500 miles between oil changes. Yet you'll still hear the 3,000-mile figure quoted widely, especially by people trying to sell you oil. No less an authority than Consumer Reports has debunked this myth, stating that unless you drive your car under unusually difficult conditions, and especially if you always drive it in stop-and-go traffic, going 7,500 miles between oil changes shouldn't harm your engine in any way. 

What about engine oil additives? These "additives" have already been added before you buy the oil. Any reputable brand of motor oil will come with additives that improve its viscosity index, remember what I mentioned about about the range of temperatures under which it flows properly through the engine. And that give it detergent properties that keep your engine free of sludge. Most will also include rust retardants to prevent corrosion and chemicals to protect metallic surfaces.


With all these additives already in the oil, putting in more may actually dilute what's already there and lessen the oil's effectiveness. Check your car's manual to see if it has any special additive needs, but this is unlikely in anything except some of the most exotic high-performance engines. 

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1 Comment

Reply Master
9:00 AM on June 12, 2017 
As you wrote, we should check oil status of car, but on our van, which we barely use or use it like a ad for our page ( https://www.misaron.si ) ,
we only check oil before registration date :))
And it still runs!