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Is there an Advantage to Synthetic Oil?

I know with regular motor oil mechanics advise to change it every 3k to 5k miles and at least twice a year even if you don’t drive much. I have heard that with synthetic you can go 6k to 8k without changing it but I don’t know about time parameters- Can you go up to 12 months if you don’t drive much? Are there any performance advantages to Synthetic Oil over Non- Synthetic?

In a standard passenger car there is no real advantage. You would not want to stretch the change intervals beyond the manufacturer’s recommendation regardless of oil type.

If the owner’s manual specifies synthetic, however, it should be used exclusively.

When I was driving my car less than 5k miles annually I changed its oil once a year and never had any problems using regular motor oil.

Claims of improved mileage or performance by switching to synthetic are usually too small to measure.

To repeat what mcparadise wrote. It is better, but unless your car calls for it, the difference is too small to worry about.

If the owner’s manual specifies synthetic, then use it 100% of the time, but if it does not specify it, then don’t worry you can use one or the other and change oil types at will. Just don’t use regular oil in a car that specifies synthetic.

Synthetic Offers More Engine Protection During Cold Starts In “Extreme” Cold Weather Like The Winter Temperatures Where I Live And Is Recommended By My Car’s Manufacturer For This Use.

Synthetic oil is more stable at high temperatures. Conventional old-fashioned oil breaks down faster at high temperature than does modern synthetic oil.

Synthetic also offers better protection against the formation of oil sludge that can shorten engine life.

Although the synthetic oils often tout extended change intervals, I stick with 5,000 mile changes using Mobil-1 EP and a new filter in all of our family cars.

More and more manufacturers recommend or require the use of synthetic in modern new cars.


Does your car have an air-cooled engine, or a turbocharged or supercharged engine? If not, and the owner?s manual doesn?t require or recommend synthetic oil, synthetic oil is usually a waste of money, even if you do extend your oil change intervals, which I never recommend, regardless of the type of oil you use.

I don?t understand why so many people try to extend their oil change intervals. Getting the oil changed or doing it yourself every 5,000 miles isn?t that difficult. Maybe I see it as a Zen thing, but I derive pleasure from taking good care of my vehicles.


From your question, I get the feeling you’re mostly interested in extending the drain interval of your engine oil by switching to a synthetic. It’s a rather bad ideea in general.

The answer is that the vast majority of synthetics are NOT designed for extended drain intervals. Unless said synthetic specifically mentions on the bottle that it is designed for extended drain intervals ( ala “Mobil 1 Extended Performance”-link below,) you should use the synth. oil for the same period/mileage as a regular motor oil, exactly as specified in your Owner’s Manual.

Just as mcp and JEM mentioned above, there is no real/measurable advantage for using a synthetic in a standard passenger car, unless the manufacturer calls for it.

If you’re not already doing this, in the long run you’ll be better served by making sure you lift the hood and check the oil level at least every other tank of gas, than switching to a synth. oil. The forum is full of expensive mishaps/ruined engines that could have been easily avoided, had the owners lifted the hood and checked the fluids as recommended in the Owner’s Manual.

It really depends on the oil being used, and the environment in which you use the oil.

Some oils are better at handling contamination by moisture, others handle gasoline contamination, and others are better at cleaning sludge and carbon build up in an engine.

If your car sits outside, and only gets used once in a while, for only a couple of miles every couple of weekends, and you live in a high humidity place, you’re going to need an oil that can handle moisture and fuel contamination.

I believe it was oldschool who posted pictures of an oil pan that one of his client’s vehicles where the oil wasn’t changed in about a year, but the car was only used for a couple of miles on random weekends, and the car was never brought up to temperature during its use, so the moisture and fuel were never being burned off.

Now, if you only use the car once a week, and you go for a 30 mile highway drive on that day, then the oil is going to get warm enough to burn off any moisture it collects, so that won’t be an issue. But, if the vehicle is running extremely rich, and is suffering from fuel contamination, you will need an oil that can neutralize the fuel the best that it can. The only true solution to fuel contamination is to change the oil.

If you live in a dry place, like I do here in Denver Colorado, then you don’t have to worry much about humidity and moisture. You can pretty much eliminate excessive fuel contamination if the car is fuel injected, and you don’t let it idle for long periods of time to warm it up before you drive it.

Unless you are using your car very hard, and getting the engine oil incredibly hot, you don’t have to worry about the oil becoming oxidized, and killing it that way, as oil won’t simply oxidize by sitting in your oil pan, doing nothing.

Anyway, you really have to look at the way you use your car in order to properly determine if synthetic oil would be of any benefit to you. Most people won’t see any benefit with the way they use their cars. Mine get used for towing, track abuse, and lots of other extreme usage, so I give them synthetic instead.


Therein lies the problem. You’re interested in extending the intervals and are under the impression that using synthetic oil gives you an automatic free pass for doing this.

An engine using synthetic may sludge up just as badly as one using regular dino oil. It all depends on driving habits, environmental conditions, etc.

You state that you don’t drive much so figure every 6 months or 4 to 5k miles at most.
Depending on the driving habits you mention, etc. then every 3/4k miles or 3/4 months may be called for.

People routinely post on this forum all of the time with engine problems and statements referring to using synthetic oil only, changed it regularly (definition can be shaky), or extending the intervals to what you mention.

Bottom line is that the use of synthetic oil does not mean an engine will go one mile further than if that engine had used regular oil.

I have no problem recommending synthetic oil for some cars. If you have roller lifters like a 4.8 Chevy V-8 I would want to help them and the roller cam as much as possible. If I had the 4.6 Ford V-8 with overhead camshafts with five feet of chain I would use synthetic. If you have twin overhead camshafts and 16 valves in a four cylinder with timing chain I recommend it. Those parts can be expensive to buy and replace.

The more moving parts, the more I like synthetic.

better protection against oil sludge with synthetic and Synthetic is always thin, it does not thicken in the cold like conventional oil does. I like synthetic in the winter because you can just go in the morning. Conventional oil doesn’t need more than thirty seconds to “warm up” but you have to take it easy the first few minutes and with Synthetic you don’t need to take it so easy.

I hate to disagree with you, but I think you should qualify what you are saying. 0W-20 synthetic oil is thinner in cold temperatures than 5W-20 conventional oil. However, 5W-30 synthetic oil is no thinner in cold weather than 5W-30 conventional oil. There is no 0W-20 or 0W-30 conventional oil. Only synthetics come with the “0W” rating.

If you want that added winter performance, don’t buy 5W-20 or 5W-30 synthetic oil. You would need something that starts with “0W.”

I Must Disagree With You. Synthetic Of The Same Weight As A Dinosaur (Old-Fashioned Conventional) Oil Flows Easier Than The Flintstone Variety. That’s Why GM Recommends It For My Climate.

GM tells me that if I don’t use the modern 5W-30 Synthetic oil then I should switch to 0W-30 for winter weather to get similar flow characteristics at cold start.

I use multi-grade Synthetic oil so that I don’t have to anticipate weather and driving conditions and switch back and forth like they did in the old days (of dino).

Do what you want to do, but I know I feel much better when I fire my car up at 15 or 20 below zero (or 10 above, for that matter) and I know I’ve got the best engine protection. Come to think of it, I like it better at +90 F on the Interstate, too.


I Have Personally Observed, When Handling Motor Oil In The Winter, That The 5W-30 Mobil-1 Synthetic Flows Easier Than 5W-30 Conventional Oil And The Manufacturer Has Testing Data To Back Up Their Statement On This Topic.

From Mobil: “Mobil 1 flows to critical engine parts quickly during cold start-ups to help protect critical engine parts from metal-to-metal friction. At 10?F Mobil 1 5W-30 flows significantly faster than conventional 5W-30 conventional oils. Furthermore, Mobil 1 has the ability to endure demanding conditions even at temperatures as low as -35?F.”

It “flows significantly faster” than conventional oil and that’s at +10?F !


What you said!

I have a generator with an 8 hp Briggs and Stratton engine. The manual recommends synthetic oil if one can not predict under what weather conditions the generator will be used. I’ve been tempted to put synthetic oil in my push lawnmower even though I obviously don’t use it in the winter. There might be some benefit with an air cooled engine that operates at a higher temperature than a liquid cooled engine.

I have a 2011 Toyota Sienna and I received a letter from Toyota that oil changes are only required every 10,000 miles. The manual specifies synthetic oil.

OP, you might as well know most answers here are guesses. Each man has his own idea he has developed over the years. If you want to really know when you need to change the oil, next time you change it, send a sample to Blackstone laboratories. They give you so much detail it is a major study to grasp it all. Not only how much goodie your oil has left, but much about the condition of your motor.

In 2009,tired of years of wild guesses all over the place on this URL, I sent in a sample of Mobil-1 EP on my 2002 Sienna, something like 160,000 miles. I held off changing it until 8800 miles to find out what the truth really is. It had enough of everything to go to at least 10,000 miles FOR MY DRIVING PATTERN, MOSTLY HIGHWAY AND SOUTH OF THE SNOW ZONE. It would not have been a good idea to go the advertises 15,000 miles. It will be different for a different vehicle and different driving conditions. I change it every 8000 miles now.

I challenged those who said there is no advantage to synthetic to run their dino oil 8800 miles, heh, heh. No takers that I know of.

Next, when I get a chance, it will be a while, I am going to put in dino oil but I am only going to run it 5000 miles, wanting to avoid any possibility of sludge. (See CommonSenseAnswers posting on this topic.) Then, I will know if it is true there is no advantage of synthetic on a standard car.

I can also say two other things. First, no one ever wrecked an engine (except maybe the drain plug) by changing oil too often, NOR BY USING TOO GOOD AN OIL. Some of the same people who tell you it really doesn’t cost that much to change the oil often seem really concerned that someone might spend a few extra bucks for a much better oil, the good synthetics. 5 quarts of Mobil-1 EP last buy was under $30 at Walmart. For 100,000 miles, now that the warranty is long gone, that oil will cost me less than $360 at current prices. That is peanuts compared to what an engine costs, or at this age, what a different car would cost.

Second, if your car is under warranty, you must comply with time/distance requirements to maintain the warranty. Also, the oil requirements if anything special.

If you want the best for your car, put in a good synthetic, if it doesn’t violate the manufacturer’s recommendation, and change it per the maintenance requirements. Test it when you change it out, not every time, but once every major season to know what it needs in the winter, then you will know more about YOUR car requirements than the finest expert on this board.

What You Said !

I Sometimes Take Advantage Of Advance Auto Parts’ Sale When They Offer A Mobil-1 / Filter Deal Every Couple Of Months. I’m sure other stores have deals, too, but I live in the sticks and am lucky to have this fine store only 20 miles away.

I stock up several oil changes worth. Let’s see . . . we drive over 60,000 miles per year and that’s just between two of us (CSA & Mrs. CSA). My daughter gets her license Saturday, so that’s another car and more miles . . . That’s a lot of changes (I do them all) and lots of oil ! I need to economize.


I use synthetic motor oil to increase service interval and reduce wear on components. My service intervals are on the 10’s. Every 10K I change the oil and filter. I have always had vehicles that take more than the standard 4 or 5 quart. If you vehicle already has hi mileage I do not suggest it. I attempted to switch an old Nissan PU once, filled it full with synth. within 2 days it was leaking from every oriface. Drained it out, back to standard 20w50 no more leaks. I also prefer synth. due to the fact most oil pans are made of alum. and have a tendancy to strip out. Not every tech that provides service uses a torque wrench when putting in yoru drain plug. After the purchase of a turbo VW pan and another for a Jeep Cherokee, I will pay the difference.

Well that is a lot of information from everyone. I have always used standard oil and have been good about checking the dipstick. Our Garage is saying to stick with Synthetic for now since that is what the car has been getting for the last few years. I will get another mechanic’s opinion. I don’t live in a cold climate- Virginia… so I don’t know how much it will save the motor.


I was wondering if the Blackstone lab tests can tell if sludge is forming in an engine?
Is there a direct link between additive life and sludging?

Or can a sludge prone engine sludge up with the oil additive package still considered in good shape?