What about synthetic oils?
Take the palms of your hands and place them together in front of you like you are praying, then spread them apart about 6 inches. That is the protection afforded by conventional oil. As the chart below shows, conventional oil turns to a jell and stops flowing at -27 F which is called the pour point and burns to a tar at 430 F which is called the flash point or oxidation point.
Now spread your hands 7 inches apart and that represents the protection offered by a semi-synthetic oil. It turns to a jell at -38 F and turns to a tar at 433 F.
Open your hands about 8" apart, that represents the protection offered by a full line synthetic which will turn to a jell at -44 F and will not turn to a tar until 482 F.
So as you can see by the chart below, as the quality of the oil gets better, so does the protection. But few of us really need an oil with a flash point of 482F, after all, by the time the engine oil gets that hot, the engine is cooked and has been destroyed anyway. Many car owners like synthetics because of the wider protection that's offered and it gives them an extra buffer zone in the event of a bad overheat or getting stuck in real cold weather.
A synthetic 10/30 oil will look and pour like water, compared to a 10/30 conventional oil which looks and pours much thicker, but I can assure you, the protection the synthetics offer is superior to a conventional oil. Besides, you will get two very important benefits from synthetic oil. You will get oil to the engine bearings quicker on cold starts where it is said much of your engine wear occurs and you will get better fuel economy because the engine isn't churning and pumping peanut butter.
Another difference between conventional oils and synthetic oils are the size of the molecules that each are made of. If you took a hand full of change (a few quarters, five nickels, 6 dimes and 22 pennies) and tossed it on a table, thats what the molecules would look like in a conventional oil. They would all be different. However, in a synthetic oil, all the molecules would be alike or all would be the size of a nickel.
Synthetic oils are our future. They are far superior to conventional oils. They flow at lower temperatures and they don't break down at higher temperatures. But I don't use them because of their cost. If I lived in Montana and my car was parked outside under a tree in 3' of snow and I had to start it at 3am to deliver newspapers, you can bet I'd have a 5-30 synthetic in my car. If I drove between Phoenix and Tucson every afternoon during the summer, I'd use a full line synthetic as well.
Many new GM cars have extended life transmission fluid and antifreeze that under normal conditions, should last 100,000 miles. I expect we will soon see oil change intervals go to 12,500 miles or so.
Will I use more oil with a synthetic? It depends on the condition of the engine, but most of the time the additional oil consumption is minor and often not measurable. If you have an old tired motor that was using a quart of 30 weight oil each fill up and you decided to change the oil to a 5/30 synthetic, then yes, because of the thinner oil and because its a synthetic, you will probably use more oil. On the other hand, if you were already using a conventional 10/30 and switched to a synthetic 10/30, there will be no additional oil consumption.
Will synthetics cause seal damage and/or make my oil leaks worse than before? Yes. If you have a pre 1980 car with any of the original seals, a newer synthetic oil can cause the engine seals to swell and leak. But synthetics do not create oil leaks. And if you all ready have a oil leak in any car, the leak will be slightly worse because synthetics are thinner.
Once I use synthetic oils, can I ever go back to conventions oils? Yes. Your engine has no idea what kind of oil or what brand of oil you use, so changing brands or quality is no problem. This wive's tale started when Arco came out in the 70' and 80's with Graphite oil and in that case, when you used Arco Graphite, you typically had a rough time using any other oil or changing brands because the graphite so contaminated the inside of the engine and threw the new oil out of specification.
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