Synthetic engine oils can cause oil leaks?

Back in the 1970s, when synthetic engine Oils (those based not on petroleum but on chemical base stocks such as polyalphaolefins) first became popular, they didn't always play well with the seals and gaskets in the car's engine. They could cause the seals to shrink in ways that petroleum-based oils did not, resulting in those messy oil leaks that would mysteriously appear in your car's parking space. Some people still fear that synthetic oil will cause leaks and so they continue to use petroleum-based oils instead.

These fears are largely unfounded. Oil manufacturers long ago learned to reformulate synthetic oil so that seal shrinkage doesn't occur. Still, there's a way in which synthetic oil can cause a leak, at least when you use it in an older car that's been operating for years on a petroleum-based oil. The synthetic oil can clean oil sludge off the seals that may actually have been blocking off tiny cracks in the seals, revealing leaks that have been there all along. This probably won't be a problem on newer cars, but if you're still driving a car that's more than, say, 15 years old, you might not want to make a sudden decision to switch to a synthetic oil.

Should you change your oil every 5,000 km, no matter what the manual says?

Once upon a time, almost every auto manufacturer recommended that the oil in your engine be changed every 5,000 km. 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 12,000 km between oil changes. Yet you'll still hear the 5,000 km 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 12,000 km between oil changes shouldn't harm your engine in any way.

Engine oil additives will improve your engine's performance ?

This is true -- except that 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 -- 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.

وهذا صحيح - إلا أن هذه "الإضافات" سبق أن أضيفت قبل أن تشتري الزيت. وأي علامة تجارية ذات سمعة طيبة من زيت المحركات تأتي مع الإضافات التي تعمل على تحسين مؤشر اللزوجة - نطاق درجات الحرارة التي بموجبها يتدفق بشكل صحيح من خلال المحرك - والتي تعطيه خصائص المنظفات التي تحافظ على المحرك الخاص بك خالية من الحمأة. سوف تشمل أيضا مثبطات الصدأ لمنع التآكل والمواد الكيميائية لحماية الأسطح المعدنية.

مع العلم أن كل هذه الإضافات الموجودة في الزيت، أن زادت أكثر من اللازم قد تضعف و تقلل في الواقع من فاعلية الزيت

راجع دليل سيارتك لمعرفة ما إذا كان هناك أي احتياجات خاصة من الإضافات، ولكن هذا غير وارد في أي شيء ما عدا بعض محركات عالية الأداء