Specs say 75W-90. Can I use 80W-90 instead?

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29
Location
Midwest
I need to buy a whole lot of gear oil for my Toyota Tundra 4x4. Specs say I should use 75W-90, but I can get a great price on bulk by the gallon of 80W-90. Is this difference in viscosity significant enough to worry about? PLEASE...real world experience and/or sound theory, not supposition.... THANKS
 
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hal

Messages
393
Location
NC
might be a little harder shifting gears when the tranny is cold (unless this is for a diff app, not sure here). Should be fine, though. I personally would go with whichever is the synthetic.
 
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4,844
Location
Saskatchewan
Is this for the differential? A GL-5 has a more robust additive package than a GL-4 and is better for the high loads in differentials, so go with GL-5 for that. A 80W-90 GL-5 passes the same high-temperature specs as a 75W-90 GL-5, so it would be okay to use in a warmer climate. It will be quite a bit thicker than a 75W-90 until it warms up though, so fuel economy will suffer. It is likely more economical over the service interval to use a 75W in a light truck in all but the warmest climates, but that would depend on a number of factors, so I couldn't say for sure. 80W becomes pretty much solid around -15F, while 75W won't reach that thickness until around -40F, so if you see those kinds of temperatures, go with 75W.
 

dnewton3

Staff member
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8,459
Location
Indianapolis, IN
I concur. Your "midwest" moniker in your signature doesn't really describ much for us. If extreme cold is not an issue, than the 80w-90 will suffice in GL-5. If very cold temps are probable, you might consider the 75w-90 instead.
 
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1,067
Location
Northern, NY
Just curious - Why do you need "a lot" of gear oil for this vehicle? Frequent changes due to water contaimination? 80w90 was the lube of choice for decades in everything from passanger cars to heavy equipment, it will work just fine in your differentials.
 
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5,466
Location
Buckley, Wa.
Use the 80w-90. My whimpy little Ranger pickup calls for 75w-90 as well but put in the 80w-90 instead. Absolutely ZERO difference in MPG or 'feel'. We are talking a bunch of heavy gears in the rear end so if anybody notices any differences from a 75w to an 80w....well, they must have the senses of a superman. Like I say.....do it with no worries and your Toyota will be well protected.
 

Arbuckle

Thread starter
Messages
29
Location
Midwest
 Originally Posted By: Rob_Roy
Just curious - Why do you need "a lot" of gear oil for this vehicle? Frequent changes due to water contaimination? 80w90 was the lube of choice for decades in everything from passanger cars to heavy equipment, it will work just fine in your differentials.
Thanks. Front, Rear and transfer case = more than 6 quarts.
 
Messages
27
Location
NY
Maybe only if it's used in real cold temperatures. I think the difference in minor for "government work."
 
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3,742
Location
Northern California, USA
 Originally Posted By: Arbuckle
PLEASE...real world experience and/or sound theory, not supposition.... THANKS
For GM rear ends, there is a rumor (I was told be someone at the dealer) that the 75w-90 synthetic is needed so there is no damage to the carbon friction plates. I don't know if the standard gear oil will attack or soften the plates. I really liked the Swepco brand 80w-90 blue gear oil in my Porsche and wanted to use it in my truck. That is why I asked the dealer if it could be used. I can't rely 100% on the service tech. I never called GM to confirm whether or not it could be used. GM says it's OK to use 80w-90 in the front axle of my truck, so there may be something to the carbon disks getting damaged by non-synthetic fluid. http://www.swepcousa.com/lubesite/products/h201.htm
 
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3,023
Location
USA-Michigan
 Quote:
This bulletin is being issued to inform dealers about the compatibility and usage of the new Fuel Efficient SAE 75W-90 Synthetic Axle Lubricant, GM P/N 12378261 (In Canada use P/N 10953455), with current axles, and with the non-synthetic axle lubricant, GM P/N 1052271 (In Canada use P/N 10950849), for the rear axles on the above light-duty trucks. Testing has shown that the new synthetic lubricant will chemically attack the Room Temperature Vulcanizing (RTV) sealant. Use only the non-synthetic lubricant, P/N 1052271, in axles using RTV sealant (See 9.5 and 10.5 information below). American Axle and Manufacturing (A.A.M.) has approved the use of the new Fuel Efficient SAE 75W-90 synthetic axle lubricant for rear axles with the following restrictions: All 8.6 inch axles are compatible as originally built. 9.5 inch axles on vehicles built prior to mid-February 1998 are NOT compatible because RTV sealant is used on the cover pans. On vehicles built after mid-February 1998 and equipped with 9.5 inch rear axles, synthetic lubricant, P/N 12378261, can be used because the RTV was replaced with a gasket. Other mid-February changes to the 9.5 inch rear axles include a new cover pan and cover pan fasteners common to other axles. Important The new cover pan is not retro-fittable to the housing of 9.5 inch axles on vehicles built prior to mid-February 1998. A new retrofit kit is available that will enable the use of synthetic lubricant for vehicles built after mid-February, 1998. All 10.5 inch axles prior to March 3, 1999 are compatible if the axle shaft hub seal (RTV) is replaced with P/N 327739 gasket when changing to synthetic lubricant. As a product improvement, this new lubricant has been released into 1999 current production C/K vehicles built after the above VIN breakpoints (Except HD3500 models which use 75W-140 synthetic lubricant, P/N 12346140). It is recommended that synthetic lubricant be used when changing rear axle lubricant for the following reasons: Potential fuel economy Lower operating temperature under severe usage conditions Important You do not need to wash/rinse any non-synthetic lubricant from the axle cavity when changing over to a synthetic lubricant. However, you should remove debris from the magnet and the bottom of the axle cavity whenever the axle fluid is changed. On light-duty trucks equipped with locking differentials, do NOT use a limited-slip additive.
 
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4,844
Location
Saskatchewan
 Originally Posted By: andrewg
Absolutely ZERO difference in MPG or 'feel'. We are talking a bunch of heavy gears in the rear end so if anybody notices any differences from a 75w to an 80w....well, they must have the senses of a superman.
You'll never be able to physically feel a percent or two improvement in fuel economy, nor would such a small change be statistically significant in a driver's fuel economy records, but it doesn't take much to pay for the difference.
 
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1,010
Location
South East Asia
 Originally Posted By: rpn453
 Originally Posted By: andrewg
Absolutely ZERO difference in MPG or 'feel'. We are talking a bunch of heavy gears in the rear end so if anybody notices any differences from a 75w to an 80w....well, they must have the senses of a superman.
You'll never be able to physically feel a percent or two improvement in fuel economy, nor would such a small change be statistically significant in a driver's fuel economy records, but it doesn't take much to pay for the difference.
I would think differently, for gear oil improvement can be noticed easily, even though the change may not just from viscosity change. This can be changing from mineral to synthetic oil and loads of EP and friction modifier like moly also made noticeable fuel economy improvement.
 
Messages
5,466
Location
Buckley, Wa.
 Originally Posted By: kr_bitog
 Originally Posted By: rpn453
 Originally Posted By: andrewg
Absolutely ZERO difference in MPG or 'feel'. We are talking a bunch of heavy gears in the rear end so if anybody notices any differences from a 75w to an 80w....well, they must have the senses of a superman.
You'll never be able to physically feel a percent or two improvement in fuel economy, nor would such a small change be statistically significant in a driver's fuel economy records, but it doesn't take much to pay for the difference.
I would think differently, for gear oil improvement can be noticed easily, even though the change may not just from viscosity change. This can be changing from mineral to synthetic oil and loads of EP and friction modifier like moly also made noticeable fuel economy improvement.
Perhaps some differences would be noticed in regard to MPG if going from dino to synthetic....and that's a big MAYBE. But my main point was if all things are equal, and one went from a 75w-90 to an 80w-90...it would be impossible to notice any difference. When I recently went from a dino 75w-90 to a synthetic Amsoil 75w-110 I noticed no difference. But I didn't do it for any reason other than the long-term protection and security I get from using a high quality synthetic.
 
Messages
25
Location
Texas
I just bought a 5-gal pail of Mobil Delvac 75w-90 synthetic to do front and rear diffs on my Dodge CTD. $110 out the door. Is that a good price?
 
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3,742
Location
Northern California, USA
 Originally Posted By: hogpops
I just bought a 5-gal pail of Mobil Delvac 75w-90 synthetic to do front and rear diffs on my Dodge CTD. $110 out the door. Is that a good price?
$110/20Qts = $5.50/Qt = Good Price
 
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