80w-90 or 85w-140 Which and Why ???

Discussion in '6.9L IH & 7.3L IDI Diesels' started by MIDNIGHT RIDER, Oct 11, 2017.

80w90 or 85w140

  1. 80w90

    2 vote(s)
    16.7%
  2. 85w140

    5 vote(s)
    41.7%
  3. Synthetic

    5 vote(s)
    41.7%
  1. MIDNIGHT RIDER

    MIDNIGHT RIDER Full Access Member

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    Like the title says, 80w-90 or 85w-140 gear lube, which do you run and why ?
    The book specifies 80w-90 GL5 (plus limited slip additive if a L/S)
    I have found the price to be the same from most sources/brands, so cost should not be a factor.
     
  2. Mulochico

    Mulochico Supporting Member Supporting Member

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    80w-90 front, 75w-140 rear.

    Rear gets more of a workout so more heat. This equates to thicker lubricant. Could be wrong, but that is the most consistent info I have gotten over the years. Thinner for better mileage, cooler temps.
     
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  3. Thatoneguy

    Thatoneguy Full Access Member

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    It really depends on what you do with your truck. Tow a lot, run massive tires, etc, 140. Occasional towing, but mostly just regular driving, 90 is good. Both have the ability to provide good lubrication under stress. Really just depends how fast they're gonna need to change it again. 140 will hold up to hard work a lot longer before breaking down.

    Sent from my VS980 4G using Tapatalk
     
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  4. Black dawg

    Black dawg Registered User

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    75w140 syn is good stuff.

    A few years ago I put a us gear overdrive in my truck, it worked great, but after about 100 miles loaded, it seemed too noisy...and could smell gear oil (80-90). My first thought was thicker oil, and put in heavier non synthetic gear oil. This actually made it worse, and it hit me that it must be getting too hot.

    added 75w140 synthetic, and it has been flawless ever since...minimal noise, and no smell ever.
     
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  5. MIDNIGHT RIDER

    MIDNIGHT RIDER Full Access Member

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    Thanks; I wish I had of thought to add synthetic as an option in the poll (this is my first poll ever).

    Your comment about the smell made me think of something that hadn't occurred to me before; the one memorable thing about plain old gear lube is that unmistakable smell; if you have ever got a whiff of it once in your life, you will know exactly what it is if you ever smell it again.
    If you walk past your vehicle and catch scent of that odor, you will definitely know that something is amiss and investigate to find out what is leaking.
    Does synthetic gear lube have that same smell ?


    Another question about synthetic gear lube: I have often read that synthetic engine oil is much "thinner" and will leak out of a leaky engine much more quickly that plain old oil; does the same hold true for synthetic gear lube ?


    On EDIT: I just figured out that I could edit the poll; so, I added synthetic as a choice.
    If you have already voted, it will allow you to change your vote (and you don't have to wait four years to do it)
     
    Last edited: Oct 12, 2017
  6. Black dawg

    Black dawg Registered User

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    The Valvoline gear oil that I use smells very similar to me, syn or not.

    I have never had leaks develop after switching to syn gl, and the 75w140 is much thinner cold/flows much easier cold, than 80-90w
     
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  7. Thatoneguy

    Thatoneguy Full Access Member

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    I have also heard such things about synthetic oil in general... Does anyone have any experience about whether or not an old motor will start leaking more if you switch it to synthetic?

    Sent from my VS980 4G using Tapatalk
     
  8. chillman88

    chillman88 Supporting Member Supporting Member

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    I started running synthetic on and off in my old Chevy after about 170,000 miles. I don't know what the P.O. used. No new or worse leaks to be found. Last I looked the odometer was around 212,000

    From what I've read the main issue people were having was in neglected, dirty engines where the synthetic was cleaning away sludge build up, and then leaking. Basically, they weren't far from leaking even on non-synthetic oil.
     
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  9. Thatoneguy

    Thatoneguy Full Access Member

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    Gotcha. I've thought about trying it in my truck... But I bought it at like 230k miles. The motor is still healthy and everything and I have no real reason to suspect it was not maintained well, but I don't want any more leaks than I have lol. I got a slowly leaking valve cover and the oil cooler.

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  10. Dieselcrawler

    Dieselcrawler i pooped today! Staff Member

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    this^. synthestics will clean an engine quickly, taking away any dirt and sludge stuck around seals and gaskets.


    i wont vote above, as for me it depends on the truck. my tow pigs normally get the 75-140 syn in the rear and front.
    my off road truck gets the cheapest 80-90 available since it gets ruined quickly due to water.
     
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  11. chillman88

    chillman88 Supporting Member Supporting Member

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    I did run 10w-30 semi-syn rotella for one change in my IDI with 175k on it. No problems.

    I can't help but share a laugh with y'all. One day talking to one of the local "parts guys" he told me it was ok to run ATF in the rear. He did it all the time in his "race cars" Lets just say I never wasted time talking to him again. Some people are really not very bright...
     
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  12. Thatoneguy

    Thatoneguy Full Access Member

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    I guess I'll just have to try and it and see if it starts leaking more. Maybe ill wait until ive got new valve cover gasket in and resealed the oil cooler.
     
  13. snicklas

    snicklas 6.0 and Loving It!! Staff Member

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    On switching to synthetic......

    The 91 Jetta Diesel I just sold, first oil change after I bought it at 295,000 miles was to Chevron Delo 5W-30 Full Synthetic. Mainly because I run that on the 6.0 which takes 15 quarts and the Jetta took 5. So 5 gallons to do both.

    Before the first change I drove it long enough it consumed a bit of oil, but nothing alarming. After the change it consumed no more than it had. It was still running synthetic when it left last month with no more consumption than before.
     
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  14. Garbage_Mechan

    Garbage_Mechan Garbage Mechanic

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    85w140 syn is the way to go, still better cold flow than regular 80w90 and much better protection.

    BTW the reason GL5 gear oil or "Hypoid" gear oil literally smells like hell is the sulfur that is required to accommodate the sliding motion of the ring and pinion. It also why a little moisture in a gear compartment results in such voracious rust......the sulfur reacts with the moisture resulting in sulfuric acid formation.
     
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  15. MIDNIGHT RIDER

    MIDNIGHT RIDER Full Access Member

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    That is interesting to know and reason enough to stay out of mudpuddles and creek crossings; I have seen old rear-ends laying around with the cover missing and standing full of a grease and water mixture --- the color of that rust is completely different than normal rust and now I know why.



    As for the lube choices, sometimes us paupers have to go with whatever our meager means will allow; so, I did a bit of price research --- not an all out comparison, just a good idea of what the different lubes may cost.
    Surprising to me, a popular mail-order racing supply had a better price than any of the chain stores I checked.
    Plain old Lucas 85w-140 (or 80w-90; the price is the same) will set you back $25/gallon
    Lucas 75w-140 synthetic is almost double at $46/gallon
    One of the chain gang did have a MasterPro 80w-90 at $16/gallon
     
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