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Why only fully synthetic engine oil?

30K views 22 replies 11 participants last post by  411k 
#1 ·
I've read several times that the Murano requires fully synthetic engine oil. I am now using 10w40 instead of 5w30 as it improved engine knock under acceleration and also reduced oil consumption. However, 10w40 fully synthetic is quite expensive, like $10 a quart. There are much cheaper 10w40 oils, but they are synthetic blends, which I understand are not fully synthetic. What would I expose the engine to by using a synthetic blend instead of fully synthetic?

Thanks in advance for the help!
 
#2 ·
No where does it say the Murano requires synthetic oil, full or blended. It's a matter of choice. Many like myself choose to use it because of the benefits to the engine over the long hall. I change mine around every 5,000 and do tire rotation at same time. I buy a 5 qt jug of Mobil 1 5w30 at Walmart for 25 bucks. If you want, do a quick search for syn oil and you'll have tons of opinions to read.
 
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#3 ·
I do same, 5w30 Fully Synthetic and change every 6,000-7,000k at most. I now have 150k miles on the car and add oil before each change just to make sure I'm not running low. I am not sure about knock but otherwise my car has been running smooth on the 5w30. I dont see myself changing it up unless I heard there were tremendous benefits from it for out specific car/engine.
 
#4 ·
Not to be unkind, but there are hundreds of pages on the web explaining why synthetic motor oils are superior in many respects to conventional oils. I recommend doing appropriate homework by visiting Amsoil's website - they were one of the first companies to market synthetics widely and they know their stuff. Smart car owners have been using synthetics since the 1970's and there is plenty of information about the advantages of synthetics.

It should be sufficient to know that the manufacturer recommends only full synthetic oil. That should be enough info to know what a blend, although very darn good oil, does not meet the manufacturer's warranty, nor does it meet the requirements of the engine design.
 
#6 ·
That's fine if the manual says so.

Of course, the more demanding manufacturers like BMW and Chevy in the Corvette have specified synthetic for years. It's all I have used since 1977. I can't imagine any reason not to use it provided that I wasn't simply unable to pay for it.
 
#7 ·
That's fine if the manual says so.

Of course, the more demanding manufacturers like BMW and Chevy in the Corvette have specified synthetic for years. It's all I have used since 1977. I can't imagine any reason not to use it provided that I wasn't simply unable to pay for it.
I have always wondered if this is driven by the engineering or marketing guys. I suspect it is the latter.

Years ago some up and coming Sales and Marketing guy came up with the idea to supply Chevy with bulk Mobil-1 at a significantly reduced cost if Chevy would simply "recommend" their oil and enable Mobil-1 to advertise their oil as standard equipment on all Vettes. A stroke of genius. Now some kid driving a 10-year old Chevy Chevette figures if Mobile-1 is good enough for a Corvette then it would be great for his Chevette.

-njjoe
 
#8 ·
I don't blame you for having reservations about that. In fact, conventional modern motor oils are very good, and they are considerably better than was the case 20 years ago.

However, a bit of research will reveal advantages of synthetic oils:

- Better resistance to breakdown under prolonged heat or overheating (great protection for the engine if you have a thermostat lock up or a radiator hose blow)
- Better wicking throughout the engine, including on the bearing surfaces that are exposed to wear at cold starts (a benefit at every start)
- Better resistance to film breakdown under high pressure at metal-to-metal interfaces
- Polymer chains that hold up longer under extended service, preserving the oil's ability to maintain proper lubrication (making it easier to extend change intervals)

There are other reasons, but these suffice. Aside from marketing blurbs, I've been reading oil tests for 30+ years and at least for me, the evidence is sufficient.

The exception I've made to running full synthetic oil was to run a synthetic blend in my daughter's '91 Camaro, which used about a quart of oil every 1200-1500 miles. I thought the blend was a good compromise, and that engine ran nicely for the seven years she owned it, still running great at @165K miles when we sold it.
 
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#9 ·
P-

Actually, I agree with you.

I believe synthetic motor oils are superior to dino oils when used under extreme operating conditions and can be used to extend the service interval. That is why I have been using syn in my MO since it's first oil change.

-njjoe
 
#10 ·
I just read the owner's manual (I should have started with that) and it says NISSAN recommends mineral oils, 5w30 for cold weather and 10w40 for warmer ones. That Murano takes about. 1qt every 1000 miles so by the time I change the oil I had time to pour quite a amount. So l am going to go for some mineral or blended oil and change it every 7500 miles.
 
#11 ·
Given that oil consumption, running a synthetic blend would make a lot of sense to me. Probably cuts the cost in half.
 
#13 ·
I'd love to know why my 2012 Manual says to change oil every 3750 miles? Seems a rather short period of time with today's oils. I'm getting about 8350 on my 2014 Ford Explorer's intelligent Oil Monitor and I drive exactly the same way, and the same places with both cars. Same size engine, too 3.5L.

Is that just a marketing ploy on Nissan's part?
 
#19 ·
Half a cup (0.125 qt.) between oil change is nothing. You can't even reliably measure the quantity with the dipstick. If you fill the oil to the full mark, it will still be near full next time you change the oil.
My 05 has 171,000 miles or 275,000 km, and it loses a quart of oil every 3000 miles, or 2 qt. between oil change. It leaks mostly at the valve cover gaskets.
 
#21 ·
i have oil leak from a second oilpan according to my mechanic!
he could not fixed the car and asked me to take to the expert, now i do not have time for it i was wondering whether i can use fully synthetic 5W30 or 10-W40 to add on. i have just changed to new oil only about 1 month ago. mileage incredibly at 422,000 km aprox. 262,000 miles .
 
#22 ·
Yes, you absolutely can, and it's the best oil you can run. If it hasn't been run on synthetic all its life, I'm very surprised.

Just use the weight the owner's manual recommends.
 
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