My car is a 2006 Infiniti M45. It has a high power V8 engine.  I live in a climate with very hot long-sustaining  temperatures in Summer and very cold temperatures in Winter.

I have broken in the engine and now want to change from 5W30 dino oil to 5W30 synthetic.  There is so much advertising by oil companies that portray their product as being the best.  Example, Mobil 1 says they are the best; AMSOIL says they are the best.

Please give me your recommendation as to brand of synthetic oil I should buy and if the 5W30 should be changed.

Thank you  

First,you should see what the dealership recommends.

Secondly,you should ask other people with the same type of vehicle or brand of vehicle you have what they are using.

Third,be aware that once you start using synthetic oils you should continue using them for the life of that motor so choose wisely.

Fourth,synthetic motor oils are VERY EXPENSIVE.

If you are not changing the oil yourself or think in the future you will have a place like Jiffy lube or the dealership change it,you will hve to see what they are selling to do the job.

Most places will not take the oil you bring in and change it for you.

They want to charge you for the oil so they can makea little extra money.

The most widely used and availible synthetic motor oil on the market has to be Mobil One.

It is an excellent motor oil,used by many racing series across the planet.

It is very slippery and will maximize your fuel mileage.

Castrol's SynTec sythetic motor oil is also an excellent motor oil.

It is a different design of synt oil from Mobil One-not as slippery and it has a design that makes it stick to engine parts and for good reason-it helps to protect the engine in that way.

Unfortunately,compared to Mobil One,it will not get you as great a gas mileage advantage as Mobil One.

But I've used this motor oil (Castrol Syntec)and continue to do so in all my vehicles-1989 Nissan Pickup truck-1999 Honda Accord 4 cyl.-2003 Honda Accord 4 cyl-2000 Dodge Caravan(work van)-2000 Toyota Echo-2002 Murray lawnmower-2002 Lawn boy lawnmower

Originally I used Mobil One in the Toyota Echo and it got INCREDIBLE FUEL MILEAGE.

I had two tanks early in the life of this Echo were as high as 46 mpg!

But Mobil One has a smell to it and I have had really good experience with Castrol Syntec so I changed to that in the Toyota as well.

Long story short-it still runs as well but the mileage dropped to a maximum of 40 mpg.

I have a faith in Syntec that I don't have in Mobil One simply because of the 245,000 miles we have on the NISSAN pickup that still runs almost as good as new.

These cars run very smooth once warm and part of that,no doubt,is that most synthetic motor oils run much,much cleaner than conventional oils.

As far as using AMSOIL or this other brand Purple something,I can only recommend yu check the internet for users who have used it before.

I just put Valvoline Synthetic automatic transmission in the 2000 Dodge Caravan and it made a dramatic improvement in the shifting of the transmission-I've used some Valvoline products over the years and never heard anything bad about their products-good stuff also.

Quaker State also has a line of synthetic oils on the market.

After a regrettable series of issues with their products surfaced about fifteen(?) years ago,this company became determined to regain their good name and their recent products seem to prove they are really bringing good products to the market.

Pennzoil also has a great line of synthetic products on the market.

So your decision is NOT an easy one.

Also,remember to follow what your cars manufacturer says for the change and use intervals.

Use the weight oil they recommend and use an excellent quality oil filter.

Oil changes will ALWAYS be cheaper than engine changes.  

Thank you.  I appreciate your thoughtful and detailed comments.  

Hammatime ,
I would add three things to your post . I would also search for the manufacturers recommendation regarding the oil . Never use an oil filter other than the manufacturers , at least during the warranty period. And lastly , regarding cost , yes synthetic oils are more expensive than mineral based oils but they do not require as frequent changing .  

I am going to offer my two cents, if I may. Consumers Reports tested 60 NY taxis a number of years ago, 30 with regular oil and 30 with Mobil 1. They started with the cars new. After 60k miles, the cars with regular oil showed normal wear, expected in a car driven hard and often. The cars using Mobil 1 show "NO APPRECIABLE WEAR". As to the increased cost, most of us using petroleum-based oils change our oil more frequently than the mfr's recommendations. What I did was lengthen my change frequency to offset some or all of the extra cost of Mobil 1; however, while in mfr's warranty, I never exceeded their requirements. The net result is that the cost per mile of the Mobil 1 oil change over the longer miles between changes (say, 6,000 miles instead of 4k) was not a lot more than regular oil. The reality is that synthetics oils NEVER break down. They get dirty but never lose their capability to protect your engine. Petroleum-based oils do. Mobil 1 also bonds to the metal, protecting it when you start it cold, which is the worst thing you can do to an engine.

By the way, there is a reason when you change the oil on a Porsche, Mercedes, Viper or Corvette and you see the words "Only use Mobil 1".

Not sure about the smell and I don't care. Mobil 1 works. Good luck to you  

Indeed,Mobil One is far and away the most popular synthetic oil on the market today.

And,you can find it anywhere in the United States I'll bet.

This becomes very important after you break in a car motor with synthetic because after you do,everything I ever heard has said that you should use that same oil for the life of the motor.

And I do have proof that Mobil One in a Toyota Echo,at least,really helped that little car get incredible gas mileage.

Kind of makes me wonder if using Castrol Syntec was the right way to go but hey,I've already made that decision so I have to live with it.

Doing things over in a car that I was going for maximum gas mileage in,I might well choose Mobil One.  

I use Castrol Suntec in my Honda CRV and another brand synthetic in my Honda Motorcycle.  Both engines run smoother and have better acceleration.  If you consider the extra cost to be a problem, I was shocked that Pep Boys is offering a Castrol Syntec 5 quart oil change with filter for $24.95.  That is quite a price!  

Redline...better than Amsoil, Mobil 1 or any other synthetic. No, I don't sell the stuff, but I used it on recommendation of Tri-Point Engineering, a Mazda team car facility and repair shop.

The stuff is awsome.

Oh, and while you're at it, use Motul in the gearbox.