Diff oil: 75w-90 or 75w-140?
https://g35driver.com/forums/2340501-post35.html
Originally Posted by Hydrazine
Hi Mike,
I was certaint of it based on my own design testing, but after testing yours on your car, I was convinced they don't work at all.
Remember, after we uninstalled yours, your car dynod exactly the same on all parts of the curve.
And yes, I am sure it was the ECU. Even before testing, I explained ECU changes can happen. And they typically move upward after a few pulls on the dyno and reach a plateau.
If the TB spacer was making gains, your car would have lost power after it was removed. But it didn't.
For the ones that did show gains, I would give it a second thought if they were consistant in their magnitude and RPM. But they haven't.
Without strict testing controls, you could take a fleet of cars, dyno them all, and redyno them 30 minutes later and the vast majority of them will dyno higher the second time around. The ECU needs to be normalized for both sets of tests for the test to be valid.
I'm not bashing, taking sides or trying to rain on any parades. I'm just saying what I know from test experience.
And believe me. If there was any real HP to be made from a TB spacer, I would exploite its engineering to the max. ...But its just not there.
Tony
EDIT: I was going to stay out of this thread but when I saw reference to my name and testing, I had to make some clarification. Otherwise, I'll try to avoid TB spacer threads.
Hi Mike,
I was certaint of it based on my own design testing, but after testing yours on your car, I was convinced they don't work at all.
Remember, after we uninstalled yours, your car dynod exactly the same on all parts of the curve.
And yes, I am sure it was the ECU. Even before testing, I explained ECU changes can happen. And they typically move upward after a few pulls on the dyno and reach a plateau.
If the TB spacer was making gains, your car would have lost power after it was removed. But it didn't.
For the ones that did show gains, I would give it a second thought if they were consistant in their magnitude and RPM. But they haven't.
Without strict testing controls, you could take a fleet of cars, dyno them all, and redyno them 30 minutes later and the vast majority of them will dyno higher the second time around. The ECU needs to be normalized for both sets of tests for the test to be valid.
I'm not bashing, taking sides or trying to rain on any parades. I'm just saying what I know from test experience.
And believe me. If there was any real HP to be made from a TB spacer, I would exploite its engineering to the max. ...But its just not there.
Tony
EDIT: I was going to stay out of this thread but when I saw reference to my name and testing, I had to make some clarification. Otherwise, I'll try to avoid TB spacer threads.
I know that this has gone off topic into TB spacers, but I just wanted you all to know that I have been using 75w-140 in my diff for over 10k miles and I will NEVER go back to a 75w-90. I have no complaints at all.
Why the switch? Just seems like the extra viscosity would make for more resistance and sap power.
I switched per the recommendations of 3 Nissan/Infiniti Master Technicians who are personal friends. I was hesitant to do it because everyone on the boards here lives and dies by 75w-90 per the owners manual. It was their honest opinion that it would offer more protection for the differential so I went with it. I used the BG Ultra-Guard 75w140 synthetic gear oil. It's $20 per quart but I figured I don't change the fluid but every 30k anyways.
I did not notice any difference in power but if there was one it must be negligible. I would trade extra protection for a couple horsepower anyday.
Here is my review of the products I used. I will also bump it since it seems a pertinent topic.
https://g35driver.com/forums/drivetr...-shift-ii.html
I did not notice any difference in power but if there was one it must be negligible. I would trade extra protection for a couple horsepower anyday.
Here is my review of the products I used. I will also bump it since it seems a pertinent topic.
https://g35driver.com/forums/drivetr...-shift-ii.html
Last edited by PAIXAO; Jan 5, 2010 at 01:55 PM.
If you think about it, using 75w-140 should be fine...at normal operating temps the viscosity would be in the 75-90 range. If for some reason they go sky-high -- say your are racing through the desert in the Paris-Dakar, towing a horse-trailer loaded with camels and it's 125F -- then you are still good to go! 
If you think about it, using 75w-140 should be fine...at normal operating temps the viscosity would be in the 75-90 range. If for some reason they go sky-high -- say your are racing through the desert in the Paris-Dakar, towing a horse-trailer loaded with camels and it's 125F -- then you are still good to go!
If you think about it, using 75w-140 should be fine...at normal operating temps the viscosity would be in the 75-90 range. If for some reason they go sky-high -- say your are racing through the desert in the Paris-Dakar, towing a horse-trailer loaded with camels and it's 125F -- then you are still good to go!
A 5w 30 weight engine oil is 30 weight once a certain temp is achieved and doesn't change regardless of oil temp (unless it gets ultra high).
IMHO protection is more of a function of maintaning the film thickess inbetween the two metal parts. Increased viscosity will do this. But IMHO, using a high quality synthetic like Amsoil that has a very high film thickess strength is a better way to achieve this.
Kind of an old link, but I think the short answer is 'yes':
http://micapeak.com/info/oiled.html
It does say that broad-range multi-vis oils (engine and gear) have more polymers -- this is what keeps them from thinning as much when they warm up -- and so are more prone to viscosity and thermal breakdown due to said high polymer content.
For the hard of reading, it also suggests using the narrowest range in which you anticipate operating.
http://micapeak.com/info/oiled.html
It does say that broad-range multi-vis oils (engine and gear) have more polymers -- this is what keeps them from thinning as much when they warm up -- and so are more prone to viscosity and thermal breakdown due to said high polymer content.
For the hard of reading, it also suggests using the narrowest range in which you anticipate operating.
Mods go little be little and the kids wear on sale Old Navy clothes. Pants for $3 and shirts for $2 FTW. I am fearful about how much my son will eat when he's 12+ after seeing how much he eats right now at 5.
.Kind of an old link, but I think the short answer is 'yes':
http://micapeak.com/info/oiled.html
It does say that broad-range multi-vis oils (engine and gear) have more polymers -- this is what keeps them from thinning as much when they warm up -- and so are more prone to viscosity and thermal breakdown due to said high polymer content. For the hard of reading, it also suggests using the narrowest range in which you anticipate operating.
http://micapeak.com/info/oiled.html
It does say that broad-range multi-vis oils (engine and gear) have more polymers -- this is what keeps them from thinning as much when they warm up -- and so are more prone to viscosity and thermal breakdown due to said high polymer content.
For the hard of reading, it also suggests using the narrowest range in which you anticipate operating.If you think about it, using 75w-140 should be fine...at normal operating temps the viscosity would be in the 75-90 range. If for some reason they go sky-high -- say your are racing through the desert in the Paris-Dakar, towing a horse-trailer loaded with camels and it's 125F -- then you are still good to go!
I would believe you can safely use the 74w-140 with no problems and for people in extreme heat (AZ, Vegas, etc) I would think this is a possible option but still a better option is to run the right viscosity and run an external cooler if you have issues.
Joined: May 2003
Posts: 1,820
Likes: 3
From: Warshington
Hooray for oil talk and kid talk! Plz refrain from throttle body spacer talk. But, since this is *my* thread: TB spacers on non-carburetor engines have been proven to do nothing over and over. A fringe cases exist that make for a few followers, but in testing, you throw out the fringes. If it does nothing 99 times, and adds power 1 time, you can't conclude that it works.
And, FWIW, I was readding on bimmerforums of a guy that used 75w-140 in his E36 M3 and said it was sluggish at the track.
Joined: May 2003
Posts: 1,820
Likes: 3
From: Warshington
I guess he could be a liar. Them Bimmer dudes have been known to exaggerate many things. 