Vq25Det Major Repairs

[Jetwreck]

Nissan would have been aware of the heat and pressure when they came up with the oil spec.

What was wrong with the 5w-30 you ran? Did you get a UOA?

you sure.......if your in the snow and cold all the time its probably fine! 20-40 degrees it seems silly.

5W30 was too thin and why would I bother getting it tested when it was quite obvious to me on a 50K old motor that never had a rattle before on 10W40 that it was wrong. Personally I think your crazy to run anything under a 10w40 in these unless you live in the snow.

I personally don't care what anyone runs. The what oil to run debate bores me. It's cheaper to buy the right stuff than it is to change a motor.

PS....recon nissan new about the turbo issue, Subframe issue, front bush's, ect......?

Edited August 9, 2013 by Jetwreck

[scotty nm35]

I agree, every car I have heard with engine rattles has had the standard mechanic's 5w30 (Commo spec) oil. Just remember these VQ's run 90+ degree oil temps daily, even in winter, and I have seen over 10 bar oil pressure on my gauge.

[Equilibrise]

I always ran 10w40 until this one time when the parts shop were out of it and only had 0w40 in full syn left. Call it coincidence if you like, I'm not saying that it was the sole reason for the failure, but I would definitely try to prevent the damage my engine has had.

[Duncan]

0w40 and 10w40 are exactly the same thickness once the engine is warm. the first number only applies below about 50 degrees which is about the first 2 minutes of your drive.

What did Nissan actually recommend for these motors?

[scotty nm35]

Have you ever tested that theory Duncan? Try warming a sample of each to 90 degrees, I think you will find there is a difference, especially the speed it will flow through a small hole under pressure.

Too thick an oil will obviously slow down oil flow to the cam chain, turbo, and anything else with a .9mm restrictor. Too thin will possibly flog bearings out and will drain past the drainback valve too easily causing cold start wear. If you can hear noise then there is definitely wear happening, which is why I stick to 5w40 winter or 10w40 summer. I have brand preferences also.

More importantly is to service your engine regularly. For the price of a semi synth these days ($20-$30) I would be dropping it every 4k and keeping it fresh, it's cheap insurance...

[Duncan]

Nope, never tested it.

I am just relying on the specifications published by the guys who defined the SAE standard. If you have noticed a difference either the SAE guys don't know what they were specifying, or the oil was non-compliant because the specification is exactly about a certain amount of oil going through a certain sized restrictor at the specified temperature

[MrStabby]

I have the same understanding as Duncan, but its an oversimplification to say 0w-40 and 10w-40 have the same viscosity at operating temperature, because even different 10W-40s have some variation in viscosity at operating temperature, because all oils are a bit different. The 40 rating is not a narrow range.

Example:

Redline 5W-40 = 15.1 @100DegC

Nulon 5W-40 = 13.0 @100DegC

= 16% difference

Also, the theory is that generally thinner oils protect better at startup, but thicker oils protect better at high temperatures/stresses - but only for the same quality oil.

Duncan - IIRC recommended oil is 5W-30

[Jetwreck]

0w40 and 10w40 are exactly the same thickness once the engine is warm. the first number only applies below about 50 degrees which is about the first 2 minutes of your drive.

What did Nissan actually recommend for these motors?

I'm with you Duncan about the 40 figure.....it's the 5W30 or even worse the 0W30 figure in Australia that does not suit this motor. That oil figure is for the Japanese domestic market and as this car was only released into the Japanese market things will be different. e.g. 100 octane fuel, Temperature, Humidity....and the big daddy.....Snow! They also recommend plugs with a heat sig of 5....I run 7's

"but thicker oils protect better at high temperatures/stresses" This statement only reenforces my argument for not using a 5W30 oil......We have a high boost motor(even in standard form) pushing 2T through a gearbox that sucks over 1/3 of the power and for 5-6 months of the year in the eastern states we can quite easily hit 30-40 degree's.

The Grade of oil also plays a significant part in motor wear with this thing.......Going to Bob the mechanic and getting him to do an oil change with a $5 filter and $20 can only lead to a bad ending. But what do I know.......it's not like I work on these things every other weekend.

Adam - Test the IIRC recommended oil! Go crank some more boost into the motor and take if for a thrash......then put 10W40 in and do the same thing. Let me know what you come up with..... also test it mid summer!

[PN-Mad]

Isn't the go to Nissan oil actually 7.5w30?

Btw, oil thread is over -----------------------> there.

This is a motor thread!

[joshm35]

Oils ain't oils

[Equilibrise]

Yeah it is the motor thread... oil is certainly an opinionated subject. All in all though, I have tested out low vis oil and it proved to be a very painful experience. I am still not making a definitive statement that it was the cause of the damage, but I certainly won't be risking putting the same oil in and expecting a different result. Personally I am all for 10w40.

[gleeson]

+1 for 10w40

[Equilibrise]

A few more pics including a dismantled oil pump, close ups of the chain tensioners and complete reassembled timinig assembly.

[scotty nm35]

You have the unshrouded oil pickup, I suspect the shrouded one may be better to help stop oil surge it you plan to drive it hard.

Are you upgrading anything while you are there Adam? Or will it be staying stock... Looks good mate.

[Equilibrise]

I was very tempted to upgrade a few things while I was there, but all of the other upgrades are pushing costs. What upgrades are you recommending? Where do I get a shrouded pick up from? I will be driving it hard.

[scotty nm35]

I will try to remember to look for a shrouded pickup, not sure I have one as I used the two I had here on the two engines I rebuilt. I can only assume they were modified to prevent oil surge as only half the engines have them.