Oil viscosity and highway driving

[UCSB_G35]

Hi,

I'm new to the forum. I have a question about oil viscosity and highway driving. I have a 2005 G35 sedan and I do a lot of highway driving (probably about 30,000 miles a year). The owner's manual says 5w30 is preferred but I can use 10w30 or 10W-40 if the ambient temperature is above 0 degree C. I'm in California so the the temperature is never 0 degrees. I've read on this forum that highway driving is very easy on the oil but I have also read that for extended highway driving I should get a thicker oil than 5w30. So, should I use 10w-40 or 10w30 for my car, given that it's allowed for my car and I drive so many highway miles? Thanks for your replies.

 

[darkdan]

I'd go with 10w30.

I'm not a big 10w40 fan.

Are you planning on conventional or synthetic?

 

[UCSB_G35]

Thanks for the quick reply darkdan. I will eventually switch to synthetic after or soon after break-in period. I was thinking of the new M1 Extended oil.

 

[buster]

Nice car. Much nicer then mine. I'm using Mobil 1 Extended Performance 10w30 and I also do about 23k a year, mostly highway. 10w30's tend to be less volatile and more shear stable. In cali, I'd use nothing but.

 

[DR Racing]

conventional 10w30 will not thin out as much over the OCI as 5w30 will but if you go to synthetic use 5w30 or even 0w30 GC or M1. Dan

 

[The_Jeff]

You'll be fine with a 10w30. You'll probably run close to water thermostat temp most of the time.

Nice ride. Can you get oil temp out of the onboard computer, for example, out of where the odometer normally resides?

 

[y_p_w]

If all you do is highway driving and only start at high ambient temps, a 30 weight oil might even work. A modern Group II 30 weight (like Pennzoil HD-30) will be thinner at ambient temps than a typical SAE 30 made 10 years ago.

OTOH - it's hard for a manufacturer to recommend at 30 weight because there are still some out there that will be rather thick at room temps and will give craptastic cold starting. Castrol HD30 has a pour point of 21 deg F, while the Pennzoil HD-30 is -22 deg F.

 

[Mamala Bay]

I know lot of mechanics that recommend the straight 30wt. The smarter ones use that for conventional oil The 40wt for high mileage engines in my conditions. If you are driving that much miles per year, I would think a synthetic oil would be an ideal situation for you.

The Mobil EP 10w30 is on the thin side, while Amsoil 10w30 is on the heavier end of a 30w.

Either oil would do fine. You might even consider the Amsoil 5w-40 if going with synthetic in summer heat. It's hot down here, kind of like UV heat. I've never seen so much rain(clouds also) the last 2 years here. I think the weather pattern is changing.

 

[UCSB_G35]

quote:

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Originally posted by eljefino:

Nice ride. Can you get oil temp out of the onboard computer, for example, out of where the odometer normally resides?

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I'm not sure if i can get oil temp from the onboard computer or not, still reading the owner's manual. Thanks for the compliment. Anybody looking into getting the G35, I highly recommend it. Great car at a decent price, well at least compare to it's competition.

 

[ARH_0700]

Nice car UCSB...

In Cali I would use a good 10w30 conventional. BTW as a side note- I've read that, with this engine, it's good to wait until 10k miles to switch over to syn, then switch to GC 0w30 or Mobil 1 10w30 and you should be set. I second your recommendation of the G35, it puts a smile on my face (and others') everywhere I drive

 

[ARH_0700]

Oh I forgot the

 

[Mamala Bay]

Also noted I've used the Amsoil 0w-30. That is another option and has done very well in my driving condition. MPG in savings is worth the extra cost.

It's an excellent synthetic extended OCI oil you might want to consider. It does very well in high temp driving conditions!

 

[JHZR2]

Go with 'regular' API SM Mobil 1 10w30. It gives excellent results, and youll be happy with it. Plus, its VERY available.

JMH