Motor oil viscosity

[StarPD]

I recently purchased a 2005 Q45. It was supposedly owned by the manager of the sister Nissan dealership to the Infiniti dealership (Midway Infiniti) I trade at in Phoenix. It was driven by his wife. It has no service history, as it was supposedly serviced at the Nissan dealership. The service people at Midway suspect that it was serviced with conventional motor oil, but no records are available. It had 24,424 miles on the odo at purchase.

I have always used Mobil 1 motor oil, and when the "Extended Service" formulation came out, I switched to it for the increased detergent properties. I have always used 10w30. My last Q45, a '94 Q45t didn't use a drop of oil, even on a 7200 mile extended trip.

I had the oil changed the day after buying this newer one, and put 10w30 Mobil 1 Extended Service oil in it. I consider that a flush, and now after around 700 miles, am changing it again tomorrow, Wednesday 2/14/2007.

Infiniti recommends 5w30 oil.

Since I live in Phoenix, where the temps rarely drop below 35 degrees, but in summer climb to as much as 120 degrees, and only occasionally travel to colder climates, I'm considering what viscosity to use.10w30, or 5w30?

Suggestions and recommendations appreciated.

Thanks.

[92Q45guy]

I would use 10w30. I live in the north east were it gets really cold and I've been using 10w30 with no problems. I use Mobile 1, Great stuff

[Q45tech]

In heat the low IDLE oil pressure from too thin an oil is the criteria.

30,40,50 depending on bearing clearances....................actually measuring pressure is the only way to know for sure.

[92Q45guy]

Very true!

[one ton garage]

I'd personally stick to the recommended 5w30 for now, esp considering you don't have to worry about the summertime heat just yet. But even then, with the phx heat, when using a syn like mobil1, you should be able to get away with a 5w30 w/o experiencing much viscosity change to warrant switching up to a 10w30

[szh]

I use and like Mobil 1 Synthetic 0W-40 a lot. Give a bit wider range of temps too ...

Z

[maxnix]

In TX, I use 10W-30 in winter, and substitute 2qts. of 15W-50 for the summer.

I always run a sythetic 75W-140 in the differential.

[qship96]

You guys might {or might NOT} want to read up on what mobil has done to their mobil 1 line .............it is speculated they have quietly changed from a group 4 to a group 3 basestock not pretty if true

[StarPD]

Okay, the consensus seems to be equally divided between 5w30 and 10w30. So I'm not much closer than when I started.

In view of the low mileage, I'm not sure that a hot oil pressure check at idle is necessary. I don't know what the dealer would charge me for doing such a test, but knowing their labor rate, I suspect that they would charge me for an hour or two, which wouldn't be cheap.

Doctrine has it that the thinner oils arrive at the valves and cams on cold start sooner then thicker oils, and that most engine wear occurs on cold starts. I understand that due to the different design of the cams and followers, this is more critical in the newer VK45 than in the older VH45. 5w30 then should arrive at the critical places sooner than 10w30, and the "30" part of the viscosity rating reflects a hot engine viscosity the same on both, meaning that in hot temps the engine is equally protected with both.

Considering that the newer VK45 engine consumes more oil than the older VH45, will the thinner 5w30 increase oil consumption over the 10w30?

If the "30" rating reflects the same effective viscosity in both oils, it seems that I'd be better served by using 5w30, even though Phoenix temps in winter are mild.

Of course, that presumes that oil consumption would be the same with both ratings, which is a concern.

So it look like, barring information that oil consumption with 5w30 will increase, that it's the way I should go.

More comments?

Thanks, guys. I appreciate it, and I suspect that others who might have the same questions but haven't stated them, will too. I think we are all still on a learning curve with the newer VK45 engine, and can use all the questions and answers we can get. This forum is the best source of good information, and of valid opinions of any that I participate in on the Internet. Most of the forums I contribute to arr about guns, but despite being an older guy, I love liter plus sport bikes too. Few of the forums I know of are as good as this one.

[qship96]

what does owners manual specify for your climate?

[StarPD]

qship96, any substantiation that Mobil has changed the base stock of Mobil 1 synthetic?

I'm sure I'm not the only one who would like to pursue this.

Links?

Also, the Owners Manual doesn't specify which viscosity "best". It provides a chart that indicates that either is acceptible, along with a range of ambient temps and appropriate viscosities for each range, but states in general that 5w30 is "preferred". Max tenps are the same for 5w30 and 10w30, while minimum temps are lower for 5w30. No reference is made for high speed or high load conditions, nor is there any reference regarding oil consumption according to viscosity range used, both of which are my concerns.

[maxnix]

Go to the Mobil1 website and look around. I know for the VH they specify something like a 5W-30. But if you dig around, you will discover a chart that plots required viscosity against ambient temperature, and hence I run 2 - 3 qts. of 15w-50 in the summer. Cold start then is 70° F, and warming to operating temperature is acheived in about 3 minutes.

[Q45tech]

Brand new Xw30 weight garbage $1 oil has exactly the same viscosity as Xw30 weight of the finest synthetics at 212F.

That's what the 30 means, however their might be minor differences in the range.

These viscosity numbers hold for at least 90 days and 3750 miles now beyond that it's anybody's guess.

New tight bearings will obviously operate hotter than old worn bearing so precise viscosity control is more important with a new engine than one worn in after 100-200k.

[99q45t_vl]

I use German Castrol Syntec 0W-30 with Mobil1 filter. You can get it at Autozone.

[qship96]

read all you ever want to know about oil at bobistheoilguy.com

[StarPD]

Thanks Qship96.I went there, and added it to my "Favorites".

I had my oil changed today, and for the first time ever, went to 5w30 Mobil 1 Extended Service. Used to always use 10w 30, but since Infiniti recommends 5w30, and I want to get oil up to my cams and lifters ASAP on cold startup, I figure this is the way to go.

Thanks to all for the input.

[maxnix]

I had my oil changed today, and for the first time ever, went to 5w30 Mobil 1 Extended Service. Used to always use 10w 30, but since Infiniti recommends 5w30, and I want to get oil up to my cams and lifters ASAP on cold startup,

I'd reevaluate that idea on your next change....say about May? Phoenix can be a bear for 6 months of the year.

Remember, the OEM requirement is more reflective of what's required to get the vehicle to meet EPA mileage estimates than to meet as new clearances at 100K, 150K, 200K,... miles.

With the looser oil control rings of the VK series, I would recommend monitoring your consumption carefully. If you want to preoil the valve train each morining on cold start, pull the fuel pump fuse and turn the engine for 15 seconds before reinserting the fuse and starting. there are also pressurized systems you can add.

[Q45tech]

Even in Summer cold oil [70-100F] doesn't have much lubricity.............also even at 100F it is way thicker than at 212F.

[Q_SHIP]

Even in Summer cold oil [70-100F] doesn't have much lubricity.............also even at 100F it is way thicker than at 212F.

Q45tech, what kind of oil do you use? Viscosity and weight?

[ScottJackson]

I don't think cranking the engine for 15 seconds with the fuel pump fuse out will do much to prolong engine life. If you could spin the oil pump without spinning the motor, then you'd have something. There are electric pre-lube pumps available that will pump up the oil pressure before you turn the motor over that will do the job. They're around $500. A cheaper alternative is an oil accumulator but it takes a little more effort to use and takes up more space.

[Q45tech]

The question is still: normal hot oil soon or cold oil sooner?

I use 10w40 in ATL 9 months and 0w40 [Dec- Feb] +- a few weeks either way.

[StarPD]

Not sure exacty what you're getting at. Would you clarify?

Are you saying that 5 weight cold in winter is too thin, or that 30 weight hot is? Both?

If so, would you suggest the 5w30 winter in Phoenix and 5 or 10w40 in summer? Or perhaps 10w40 year round?

Either way, I plan on sticking with Mobil 1 "Extended Service".

Oil was changed today to 5w30 Mobil 1 "Extended Service", but oil is cheaper than parts, so I can easily change it again long before the recommended OCI is up.

I DO intend on monitoring consumption while the 5w30 is in the vehicle.

Thanks.

[maxnix]

The question is still: normal hot oil soon or cold oil sooner?

Well, since oil is a non-compressible liquid, they both arrive at the same time, but does the hot oil flow (disperse) more quickly to the camshaft journals?

Sure are a lot of good arguments for warming to operating temperature.

[Q_SHIP]

The question is still: normal hot oil soon or cold oil sooner?

I use 10w40 in ATL 9 months and 0w40 [Dec- Feb] +- a few weeks either way.

Do you prefer a specific brand? Synthetic or non?

[maxnix]

He used M1 for years.

But he is an advocate of fresh oil, so performs frequent changes every 3K or 90 days. Now the clearances are looser at 300K+ miles, I believe he is using conventional per his later posts.

[StarPD]

Okay, so here's the question that gets to the heart of the matter:

Who has put 100,000 miles on the same Q with the same oil weight(s), and done a compression and leakdown test and hot oil pressure test AFTER that?

Anyone?

If so, what brand and/or type?

I have not performed the above tests, but my last '94 Q45t had 105,000 miles on it with no mechanical failures. At time of trade-in, it still got 20 mpg average in the city, and used absolutely NO oil in 3500 miles between oil changes. That was with Mobil 1 10w30 Extended Service oil, changed religiously at 3500 miles.

[maxnix]

Okay, so here's the question that gets to the heart of the matter:

Who has put 100,000 miles on the same Q with the same oil weight(s), and done a compression and leakdown test and hot oil pressure test AFTER that?

If so, what brand and/or type?

I have not performed the above tests, but my last '94 Q45t had 105,000 miles on it with no mechanical failures. At time of trade-in, it still got 20 mpg average in the city, and used absolutely NO oil in 3500 miles between oil changes. That was with Mobil 1 10w30 Extended Service oil, changed religiously at 3500 miles.

Q45tech has, at 300K and beyond. All on M1 until recently. 10W-30 I believe.

But extrapolating from the VH to the VK series is a conjecture. One can only do what one can do.

[Q45tech]

Cold ring compression vs hot ring compression vs actual idle running compression vs cruise running compression.

A little blue smoke on a 20F crank doesn't mean much with 312,000 miles.

My son and I got a real deal on 5 cases of Mobil 1 0w40 for use in C43 and Q................other than that any good 10w40 is good when changed every 90 days............even Walmart semisyn.

Changing oil frequently means you never have to say you are sorry..........since 95% is recycled into something.

[bullittandy]

Okay, so here's the question that gets to the heart of the matter:

Who has put 100,000 miles on the same Q with the same oil weight(s), and done a compression and leakdown test and hot oil pressure test AFTER that?

Anyone?

If so, what brand and/or type?

I have not performed the above tests, but my last '94 Q45t had 105,000 miles on it with no mechanical failures. At time of trade-in, it still got 20 mpg average in the city, and used absolutely NO oil in 3500 miles between oil changes. That was with Mobil 1 10w30 Extended Service oil, changed religiously at 3500 miles.

My 97 has 226K miles with on average 7500 miles oil changes (conventional) and while I haven't done a compression test, it doesn't blow ANY blue smoke until the temp drops to 15-20 degrees and then only one puff. Also no perceivable oil burning.

The previous owner used quicky oil change places so the brand was whatever they put in. I've switched at 194K to Valvoline high mileage synthetic and change the oil at 7500-10000 miles. Also use their transmission fluid.