Briefly, there are two types of "synthetic" oils on the market.
Group IV oils consist of molecules that are synthesized from simpler chemical compounds. This lets the chemical engineers "tune" the characteristics of a lubricant to exact specifications. These oils flow more freely at extreme low temperatures and don't break down at very high temperatures. As a side benefit, they generally can be specified one or two grades lighter than a mineral oil, which consumes less energy as friction inside the engine and saves fuel. These are superior products, and command a premium price.
Group III lubricants are made from reprocessed petroleum products normally left over after making crude oil into gasoline, diesel fuel, heating oil and other products (surprisingly)! They're more modestly priced, and have many of the desirable characteristics of the higher-priced spread. In much of the world outside the USA, Group III-based lubricants are not permitted to be marketed as "synthetic."
Want to use a synthetic--but experiencing sticker shock? You have two options: Hunt for sales and buy a case at a time, or use one of the synthetic "blends" which often called as Semi-Synthetic oil with a substantial proportion of mineral oil in the mix, these are priced more affordable. They also provide only a proportion of the desirable characteristics of full synthetics. Semi-synthetic oils (also called 'synthetic blends') are blends of mineral oil with no more than 30% synthetic oil.
Conventional mineral oils are simply one of the fractional distillation products from a barrel of crude, occasionally cracked from more viscous products in the refining process.
So, should you use synthetic oil? Depends. Some high-performance and high-end cars come factory filled with synthetic, and you should stick with it. If you live where it gets really frigid in the winter, you might be better off with a synthetic for its superior cold-weather starting. If you tow a trailer and your oil temperature is consistently above 200 F, you should use a synthetic oil and install an auxiliary oil cooler. I use mineral oils in my wife's car, but the race car and the motorcycles use synthetics. It's even more complicated than that--the race car gets a race-specific lubricant, with an additive package not intended for more than a few hundred miles between changes and not for very many cold starts. My Ducati, with its carbon-fiber-based dry clutch, uses an automotive-grade synthetic, while my wet-clutch Triumph uses a motorcycle-specific oil without friction modifiers. Wet-clutch bikes share the engine oil sump with the gearbox and clutch, so the friction modifiers used in auto-type oils might make the organic materials on the clutch plates too slippery and prevent good clutch lockup.
Q: After a recent trip to two major auto parts dealers for oil (5W 30), synthetic oil is slowly replacing nonsynthetic on the display shelves. The problem is, I'm getting conflicting information about synthetic oil. One store attendant told not to go back to regular oil after changing to synthetic. Then he said it would be okay to add a quart of regular oil to synthetic, if needed to top up. Another clerk said not to mix the two. At a different store, the employee said it didn't matter if used synthetic and then later replaced it with regular oil. Where is the truth?
Group IV oils consist of molecules that are synthesized from simpler chemical compounds. This lets the chemical engineers "tune" the characteristics of a lubricant to exact specifications. These oils flow more freely at extreme low temperatures and don't break down at very high temperatures. As a side benefit, they generally can be specified one or two grades lighter than a mineral oil, which consumes less energy as friction inside the engine and saves fuel. These are superior products, and command a premium price.
Group III lubricants are made from reprocessed petroleum products normally left over after making crude oil into gasoline, diesel fuel, heating oil and other products (surprisingly)! They're more modestly priced, and have many of the desirable characteristics of the higher-priced spread. In much of the world outside the USA, Group III-based lubricants are not permitted to be marketed as "synthetic."
Want to use a synthetic--but experiencing sticker shock? You have two options: Hunt for sales and buy a case at a time, or use one of the synthetic "blends" which often called as Semi-Synthetic oil with a substantial proportion of mineral oil in the mix, these are priced more affordable. They also provide only a proportion of the desirable characteristics of full synthetics. Semi-synthetic oils (also called 'synthetic blends') are blends of mineral oil with no more than 30% synthetic oil.
Conventional mineral oils are simply one of the fractional distillation products from a barrel of crude, occasionally cracked from more viscous products in the refining process.
So, should you use synthetic oil? Depends. Some high-performance and high-end cars come factory filled with synthetic, and you should stick with it. If you live where it gets really frigid in the winter, you might be better off with a synthetic for its superior cold-weather starting. If you tow a trailer and your oil temperature is consistently above 200 F, you should use a synthetic oil and install an auxiliary oil cooler. I use mineral oils in my wife's car, but the race car and the motorcycles use synthetics. It's even more complicated than that--the race car gets a race-specific lubricant, with an additive package not intended for more than a few hundred miles between changes and not for very many cold starts. My Ducati, with its carbon-fiber-based dry clutch, uses an automotive-grade synthetic, while my wet-clutch Triumph uses a motorcycle-specific oil without friction modifiers. Wet-clutch bikes share the engine oil sump with the gearbox and clutch, so the friction modifiers used in auto-type oils might make the organic materials on the clutch plates too slippery and prevent good clutch lockup.
"If your vehicle is more average, you probably can drive your car well past 300,000 kilometres without needing major engine work by using the proper grade of conventional mineral oil and appropriate change intervals."But don't assume that if a synthetic is so good (read: very expensive) that you don't need to change it as often. The base lubricant may well be better, but the additive package, which can be as much as 25 percent of the volume of product in the bottle, can still become exhausted. And unburned fuel, partially burned hydrocarbons, atmospheric dirt, metal wear particles and blowby carbon particles will build up just as fast in a synthetic-lubricated engine as in one laved in petroleum-based oil. The only way to remove this stuff is to drain and replace the oil.
Years back, it is recommended to do 5000 km oil changes, but considering the improved technology in air cleaners, compression and oil-control rings and positive crankcase ventilation (PCV) in modern engines are better than ever, it might be more kilometers prior to change.The air cleaners admit less abrasive atmospheric dirt, and closely fitted rings keep blowby and particulates above the piston and out of the oil. Sophisticated PCV systems are better at purging water vapor and partial hydrocarbons from the crankcase and burning them off in the engine, so owner can lean more toward 8000 kilometers per change for most people with cars newer than about 1990 or so. As always, mileage may vary.
Q: After a recent trip to two major auto parts dealers for oil (5W 30), synthetic oil is slowly replacing nonsynthetic on the display shelves. The problem is, I'm getting conflicting information about synthetic oil. One store attendant told not to go back to regular oil after changing to synthetic. Then he said it would be okay to add a quart of regular oil to synthetic, if needed to top up. Another clerk said not to mix the two. At a different store, the employee said it didn't matter if used synthetic and then later replaced it with regular oil. Where is the truth?
A: Early synthetics got a bad reputation for leaking. This was because, despite the claims of the oil manufacturers, the seal-swell characteristics of the new synthetics were different from those of the mineral oils they replaced. If the seal-swell rate was lower, the seals shrank and oil leaked from crankshaft seals and rocker cover seals. If the rate was higher, the seals swelled a little extra and the engine was tight. Then if the owner changed back to mineral oil, or added a quart when no synthetic was to be had, things got really bad. The crank seals had become worn, in their turgid state, and then relaxed. The valve cover seals were compressed when swelled, and when the different oil was added, everything leaked like, well, an old English sports car.
Fortunately, the situation has improved; you should have no problem switching back and forth. Adding a quart of mineral oil to a crankcase full of synthetic will be fine. Read the fine print -- a lot of the "synthetics" on the market are blends containing a substantial proportion of mineral oil.
Q: Lastly, some oil manufacturers claim that their synthetic oils produced better mileage than the minerals.. Is it true?
A: It might be true at certain point, not all. Synthetic oil provide reduced degradation by oxidation. Hence, provide longer durability.
Courtesy information from Popular Mechanics and few other sources.
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