Can I use 75W-90 diff oil?
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I use the 75-140 Severe Amsoil...most because of the 4.88 and on-trail trailer pulls, etc. Otherwise I have used their 75-90 in the past. Amsoil has a different fluid for t-cases though.
Jim_Chow
V8_Fan
I bought a 5 gallon pail of Mobil 1 Delvac 75w90 gear oil with a pail pump and use that for the diffs and t-case. By the pail, it gets the cost down to $6.50/qt. It's rated for GL-5/EP:
http://www.imperialoil.ca/Canada-English/Files/Products_Lubes/IOCAENCVLMOMobil_Delvac_Syn_GO.pdf
http://www.imperialoil.ca/Canada-English/Files/Products_Lubes/IOCAENCVLMOMobil_Delvac_Syn_GO.pdf
Coming up on 40,000 mile service and will have diffs/transfer changed. I too have been considering putting in Mobil-1 but have been having second thoughts about synthetic gear oil. I have never heard of any advantage to using it and was told that Strange Engineering advices against using it in their rear ends.
I do use Mobil-1 engine oil in LC.
I do use Mobil-1 engine oil in LC.
FWIW: I ran mine for about 12-months (15K) with many miles of on-trail use...and when I drained it apart of the 4.88 install the Amsoil was very clean...I was surprised.
Jim_Chow
V8_Fan
Although the FSM specs 90 wt gear oil for the diffs, you can't buy 90wt in a synthetic. I've been running Redline 75w90 gear oil in my 4runner rear diff for the last 60K mi w/ no issues. The only difference I'd expect between synthetic and mineral-based is longevity. At least in the 4runner's 5spd tranny, normal gear oil looked shot at 21K of coastal WA and CA driving, stick would get hot if it was 90F outside. With the Redline MT90, stick is much cooler, oil still looked good after 30K mi of So. AZ driving. That had me convinced synthetic is the way to go. Also note that the FSM doesn't call for changing the diff/t-case fluids at 30K intervals unless you primarily tow. It just says to "inspect" the fluid. In all likelihood, the dino won't last nearly as long as the synthetic. IMHO, the main advantage of the synthetic is if you plan to run longer intervals or have extreme heat/cold. Since I have 3 cars to maintain and live in an extreme climate, I can't imagine not using synthetic. If you, say, live in San Diego, synthetic is way overkill in the 100 since the 100 is already over designed/over built, unless it just makes you feel better by using it!
75w-90 is a direct replacement for straight 90 weight gear oil. Synthetics by their nature naturally meet multiweight specs as do moder mineral oils which are much more highly refined than even 10 years ago.
To the guy running 75w-140, why? All it will do is cause more drivetrain drag and reduce your mileage. Towing a trailer hardly warrants a heavier gear oil.
To the guy running 75w-140, why? All it will do is cause more drivetrain drag and reduce your mileage. Towing a trailer hardly warrants a heavier gear oil.
#1) I wanted more protection during the post break in period for the new r&p.
#2) It is recommended for heavy towing...which my rig sees on occasion.
#3) No down side that I am aware of (same actual MPG with the Amsoil 75W140 vs 90w dino lube).
I've been using 75w-90 M1 gear oil in my diffs and t-box for the last 15K miles and have no complaints thus far. Also been using M1 full synthetic at 10K intervals in the engine with great results.
M1 all around both trucks.
The main concern with a multi weight is that with wear the protection of the higher number goes away. With 75-90 you will eventually end up with 75 weight when the additives are used up. If you use dino gear oil, just change it regularly.
Synthetics have more inherent protection capability, heat stability, plus a significant reduction in drag until the fluid gets warmed up. I believe synthetics are ideal for the diffs and transfer case.
I replaced my diff and tcase fluids with Redline 75w-90 and am quite happy. The fluids were last replaced by Lexus and after 30K miles the diff fluid looked good, but the tcase fluid was showing wear. I expect Redline to last longer, but I may replace the tcase at 30K just to see how it is doing. Regarding the use of the 75w-140 synthetics, the adverse impact on MPG is not much; I believe Redline indicated about 0.5 % lower MPG than with 75w-90 (i.e. negligible).
While dino gear oils depend on the oil thickness and lots of additives to give protection, synthetics are in a completely different category, so the effects are not equivalent. There are also different types of synthetics and not all are equivalent.
Synthetics have more inherent protection capability, heat stability, plus a significant reduction in drag until the fluid gets warmed up. I believe synthetics are ideal for the diffs and transfer case.
I replaced my diff and tcase fluids with Redline 75w-90 and am quite happy. The fluids were last replaced by Lexus and after 30K miles the diff fluid looked good, but the tcase fluid was showing wear. I expect Redline to last longer, but I may replace the tcase at 30K just to see how it is doing. Regarding the use of the 75w-140 synthetics, the adverse impact on MPG is not much; I believe Redline indicated about 0.5 % lower MPG than with 75w-90 (i.e. negligible).
While dino gear oils depend on the oil thickness and lots of additives to give protection, synthetics are in a completely different category, so the effects are not equivalent. There are also different types of synthetics and not all are equivalent.
75w-90 is recommended to be used for manual transmation .
when i read arb locker manuals they recommend 90 or 140 depend on temp..... shell & mobile 1.
but its not 75w 90 its 80-90 .
when i read arb locker manuals they recommend 90 or 140 depend on temp..... shell & mobile 1.
but its not 75w 90 its 80-90 .
Sorry but that is wrong and continues to propogate an old wives tale. The second number refers to the oil's thickness at operatiing temperature. To get the first number (cold temp pumping) the oil is tested at a certain temp to not exceed a certain thickness. In the case of synthetics the homogeneous nature of the oil allows for most oils to meet the multiweight specs (note multiweight is a misnomer, the oil does not change weight) without pour point depresants. As mineral base oils have improved, they have required less and less pour point depressants and the depresants have become better quality.
For diff oil you will find there are few additives put including virtually no (and most of the time there are none) pour point depresants. As oil ages, it thickens (it is called oxidative thickning). The only time it thins is if it sheared out of grade, something that does not occure with gear oils as they are specifically designed for use in a high shear enviroment.
Jim_Chow
V8_Fan
Cary, are you saying a mineral-based 75w90 has the viscosity of a 75wt oil w/ addtives to make it behave like a 90 wt (long molecular chains subject to shearning, at least w/ engine oil) while a 75w90 synthetic has the viscosity of a 90 wt oil that behaves like a 75wt when cold?
No. Both oils are a 90 weight oil. What happens is that the Synthetics have less of a change in viscosity than mineral (broad generalization). Accordingly they are naturally "muliti-weight oils". Newer mineral oils also have naturally flatter viscosity curves because they are more highly refined (more homogenous), which makes them naturally multiweight. The flatter viscosity curve allows them to meet the low temp tests without any pour point depresants, a traditional way of making "multi-weight" oils. Check this link out for a better explination.
http://www.wearcheck.com/literature/techdoc/WZA007.htm
Cary
Cary,
I do not believe I propagaed a wife's tale, but may be guilty of a bit of exageration. Your description of the multivis gear oil fits the new condition. What I was describing is what happens as the multigrade ages. See your reference at the end of page 1 on muligrade vs monograde. The synthetics tend to be naturally multigrade, as you mention, but dino oils have additives (about 20%) which break down and cause the viscosity index (VI) to drop. I admittedly used an exagerated statement that it ends up being like SAE 75 gear oil, but still it no longer has a VI close to 90 and the protection is compromised.
In contrast, as you indicated, a synthetic or even higher quality dino will require proportionally less additives and therefore less adverse impact with wear.
In answer to Jim, I am the one who suggested that a dino oil tends to be one that performs at low temp like 75 but has additives added to make it perform like 90 oil at high temp (normally, 75 oil would be less viscous at high temp).
I do not believe I propagaed a wife's tale, but may be guilty of a bit of exageration. Your description of the multivis gear oil fits the new condition. What I was describing is what happens as the multigrade ages. See your reference at the end of page 1 on muligrade vs monograde. The synthetics tend to be naturally multigrade, as you mention, but dino oils have additives (about 20%) which break down and cause the viscosity index (VI) to drop. I admittedly used an exagerated statement that it ends up being like SAE 75 gear oil, but still it no longer has a VI close to 90 and the protection is compromised.
In contrast, as you indicated, a synthetic or even higher quality dino will require proportionally less additives and therefore less adverse impact with wear.
In answer to Jim, I am the one who suggested that a dino oil tends to be one that performs at low temp like 75 but has additives added to make it perform like 90 oil at high temp (normally, 75 oil would be less viscous at high temp).
LXPearl-
You are confusing oil thickness (its weight) and viscosity index and using the terms interchangably. As an oil ages it thickness due to oxidation (normally a by product of combustion). This oxidation causes oil to thicken. Oil does not thin as it gets older unless it is sheared down, which is unusual.
You also need to understand that the two numbers in a multiweight oil are unrelated. The first number (with a W) measure that the oil is thinner than a certain thickness (in centestokes) at a certain temperature (i.e. less than 5000 centastokes at -30f). The second number tells you the thickness of the oil in centastokes at 100c (i.e. 12 centastokes). They are measured at entirely different temps and tell you nothing about how an oil may or may not shear.
You are confusing oil thickness (its weight) and viscosity index and using the terms interchangably. As an oil ages it thickness due to oxidation (normally a by product of combustion). This oxidation causes oil to thicken. Oil does not thin as it gets older unless it is sheared down, which is unusual.
You also need to understand that the two numbers in a multiweight oil are unrelated. The first number (with a W) measure that the oil is thinner than a certain thickness (in centestokes) at a certain temperature (i.e. less than 5000 centastokes at -30f). The second number tells you the thickness of the oil in centastokes at 100c (i.e. 12 centastokes). They are measured at entirely different temps and tell you nothing about how an oil may or may not shear.
Cary,
I find your description rather confusing, but technical trivia tend to lead that direction. The same oil at two different temps (40 and 100 degree C) will have two different viscosities. I do tend to think of viscosity in terms of thickness or ability to pour. In cold weather I want an oil that hasn't thickened up so much that it is hard to turn the gears, but in doing so I don't want that same oil to be so "thin" at hot temps that it has no protection. Thus the introduction of thickners (multi-vis), anti-shear, and anti-oxidant additives in the oils. Once these are gone, the wear and tear attacks the base oil, and while the oxidation and sheared products suspended in the oil may "thicken" its appearance, the oil has lost its initial lubrication properties. I do not consider breakdown products and sludge as a viable part of oil, therefore thick black oil is not what I consider acceptable.
I find your description rather confusing, but technical trivia tend to lead that direction. The same oil at two different temps (40 and 100 degree C) will have two different viscosities. I do tend to think of viscosity in terms of thickness or ability to pour. In cold weather I want an oil that hasn't thickened up so much that it is hard to turn the gears, but in doing so I don't want that same oil to be so "thin" at hot temps that it has no protection. Thus the introduction of thickners (multi-vis), anti-shear, and anti-oxidant additives in the oils. Once these are gone, the wear and tear attacks the base oil, and while the oxidation and sheared products suspended in the oil may "thicken" its appearance, the oil has lost its initial lubrication properties. I do not consider breakdown products and sludge as a viable part of oil, therefore thick black oil is not what I consider acceptable.
