What are the pros and cons of synthetic motor oil?

This car was taken into Evans Auto Repair of Hilliard, Ohio. (Photo courtesy of member James S.)

This car was taken into Evans Auto Repair of Hilliard, Ohio. (Photo courtesy of member James S.)

Synthetic oil lasts longer than standard motor oil because it takes longer to break down, so you can drive your car longer between oil changes, says Mike LaDew, owner of highly rated Alternative Car Care in Hudson, Fla. “If you change your motor oil every 3,000 miles now, you can go 7,000 miles with synthetic,” he says.

It’s important to check the vehicle’s owner manual because some cars require synthetic. You risk voiding your vehicle’s warranty if you don’t comply, warns Sam Bell, owner of highly rated The Lusty Wrench in Cleveland. Bell says synthetic oil can also be used in vehicles that don’t require it. “The primary purpose of synthetic oils are to reduce engine wear during cold weather, and to avoid or reduce oil degradation,” he says.

The fact that synthetic motor oil lasts longer can also be a drawback. “Longer service intervals are obviously less hassle for the consumer, but if you’re like most, you’ll never open the hood between 
oil changes,” Bell says. If you develop a problem with your engine, you may drive many thousand miles without realizing it.

LaDew suggests comparing price and mileage difference. Synthetic costs about three times as much as standard oil, but can save you money on labor with fewer oil changes. “If you can save money over the long haul, then switch to synthetic,” he says. “Although some folks swear synthetic protects better.”

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Is Synthetic Motor Oil Better for Your Car?


Is synthetic oil better?
Synthetic oil costs more than conventional oil, but it's designed to last longer. (Photo by Eldon Lindsay)

With more synthetic oil products available for cars, learn about the important differences between synthetic oil and conventional oil, including the cost.


Temp is everything in the performance of all motor oils. The most friction load is at starting a cold engine. Synthetic oil works well in this area by moving oil quickly through the main bearings. Also an engine exceeding 270 degrees conventional oil will bake and glaze over engine parts, and in time will damage engine from impaired oil flow and pressure reduction. However it is best to change oil soon after a over heat. Water is boiled off faster from Synthetic oil than Conventional and less foaming.

Synthetic oil is superior by design. But be aware that not all synthetic oils are the same. Castrol Syntec is hydroprocessed mineral oil. Most other synthetic oils are composed or assembled from molecules such as ester resins. Huge difference. I have tried Mobil 1, Castol Syntec, and Royal Purple. I recommend the Mobil 1 and a good quality filter such as Wix/NAPA, Purolator Pure 1, Bosch, Mobil or similar. The cheaper filters are really not up to the job. If you use the better brand oils and filters, you can go longer between oil changes and the oil is better for the engine. Synthetic oil protects the engine through a wider range of temperatures and does not break down nearly as quickly as mineral-based oil. The bonds in the Carbon-Carbon chain are double bonds in the true synthetic oils (Mobil 1, Royal Purple, not Castrol Syntec). Stronger bonds. Synthetic oil flows more easily, has better film strength (better lubrication), and protects through a wider temperature range. Better all around. Money well spent. WalMart will do a synthetic oil change for a good price. Motorcraft and AC Delco filters are good enough. The filters and oils used at the quick-lube places are terrible. Don't do it.

I have a 12 year old BMW Z3 with 124,000 miles on it and I only changed the oil twice since it was new. Every ones notion to change the oil @ 3,000 to 7,000 miles is all hog wash. Oil does not get bad. An old time mechanic at BMW said oil is to lubricate and when it is dirty, it works the best. My car is living proof.

Synthetic oil may last longer but oil still gets dirty so even if it last longer change the filter when it's dark. Preferably add a finer filter to the system if you have the room and $. (mainly preferable on 8+qt capacity motors) If your motor oil gets dark and gritty after 3000-4000 miles and noticeably lower on the stick, it doesn't matter what oil you have, it's dirty and wearing out your motor. Ether change the filter and add more oil or change it all out. Note: The more highway miles the less you will need to change oil. If oil doesn't get dark and oil level isn't at add, your good to go even at 7000 miles. Once oil gets dirty and your at add, change it out, that's my moto.

I started using Mobile 1 synthetic about 20 years ago and I swear by it. My last car had 300K miles on it when I gave it away after 12 years, and somebody is still driving it. I changed the oil about once every 30k miles, although I did change the tiny oil filter every 10-15k. I was warned by an automotive engineer that if the car were to overheat from say a busted water hose or something and get extremely hot, that it was important to change the synthetic oil as quickly as possible. Something about it turning to acid and eating the metal? I don't know, I never experienced anything like that, but figured it might be worth mentioning.

At the local fast change oil shop, posted price for regular oil is $3.99 per qt while synthetic is $5.99. An 5 qt oil change with filter is $31.98 for regular oil and $59.98 for the synthetic. With a $2 per qt price difference shouldn't total only be $10 more ? I asked the shop and they just shrug it off. That's the corporate price policy. Same amt of oil, same filter and a double profit margin.

According to the american petroleum institute Amsoil happens to to be the top oil on the market ! His statement is self serving , apparently he is a dealer of valvoline products .

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