Is it safe to change the regular 5W-30 oil (a 2011 Nissan Versa with 28,000 kilometres on it) to the synthetic one? I had a bad experience with my previous car, a 1995 Neon – as soon as I changed to synthetic oil, it start leaking, and I had to do some gaskets reparation. I am afraid that I'll get the same experience again. – Nguyen
Not likely. I am guessing that the Neon had much higher mileage when you made the switch.
The myth that synthetic oils create leaks is just that – a myth. The smoother molecular structure of synthetic oil allows it to flow more readily, making it possible to exploit existing weak spots.
One of the advantages of synthetic oil is that is flows more readily when cold and does not thin out when hot. It thus provides superior protection during those critical early moments after a cold start. That also makes it easier for the starter to turn a cold engine over. This ability to flow more readily means it can get into any existing cracks or weak spots.
Your earlier experience of switching to synthetic oil with the Neon could have been due to age and existing cracks in seals or an earlier generation of synthetic oil which contained esters, which were hard on seals, especially those made of artificial or synthetic materials like neoprene. Later generation of synthetic oils are kinder to seals, and while they will not create a leak, they will exploit a weak spot that may have escaped the attention of the thicker regular oil.
Synthetic oils may also remove and carry away deposits that were covering a weak spot in a seal that escaped the attention of thicker normal oil. With only 28,000 kilometres on the clock, the seals on your Nissan are likely in good shape and if there is no evidence of a leak now – under the hood or on the ground where you park – the likelihood of synthetic oil "creating" leaks is minimal.
If the seals of an engine are in good shape you can switch back and forth between conventional and synthetic oils at will. Make sure to change the filter at the same time and that the oil is up to full operating temperature before changing. This will ensure you get the majority of the exiting oil out of the engine.
High-pitched sound under hood
Whenever I turn the ignition on my 1993 Honda Civic when it is cold, a high-pitched sound – similar to a pressure release – comes from under the hood. And then it suddenly disappears. What could that be? – J.D.
The most common source of such a sound is a slipping drive belt.
The belts driving the alternator, steering and brake pumps are stiffer when cold, and are more susceptible to slippage when old. As the engine turns over, the main source of power for the belts – the crankshaft – turns. If the belts are cold, it may take a moment for the heat caused by the friction between the pulley (which is turning) and the belt (which is not) – to warm up the belt enough to cause it to move properly.
Check the belts. Are they in good shape? Are they tightened properly? To gain a better idea of the source, look under the hood while you have someone start the car when it is cold. You may have to do it a couple of times to narrow down the source.
If you have questions about driving or car maintenance, please contact our experts at firstname.lastname@example.org.
Follow us on Twitter @Globe_Drive.
Add us to your circles.
Sign up for our weekly newsletter.