Synthetic vs Conventional Diff. Lube

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If my 2000 F150 is used as a passenger vehicle only, is there a huge benefit to use synthetic lube in the differential?
 
Lasts a little long and can provide a boost in MPG. Most OEMs suggest changing diff fluid around 100k or some such thing. If your doing this say every 50...id be fine with any conventional that met the spec.

Supertech syn is pretty cheap though...you may look into that
 
Not a lot difference. But the price difference is pretty small if you shop around. Walmarts Supertech 75w90 and 75w140 is pretty cheap and good quality. So I run the syn in all the diffs I work on.
 
I was a kid and the guy that raced the Ramchargers Hemi Cuda lived down the street from me. Basically he told me that synthetic diff lube was good for .14 seconds down the quarter mile. when bracket racing he would use conventional and if he had a hot race he could swap in the synth to gain that tiny bit to win the race. So yes synthetic will save fuel and not because your wallet is lighter.
 
i had a 92 dodge Dakota v6 i put in a limited slip carrier. put in stay lube syn and immediately got 20 miles per tank. that continued for the next 100k. that was huge because it had a tiny tank. i went from needing to fuel at 150 pulling the boat to fuel at a 160 and 200 empty to 220 miles. i could pull the boat down to the lake and fish and back on one tank.after that. Just barely could not make it before..

rod
 
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just like engine oils real synthetic drivetrain lubes excell! changed all drivetrain lubes to redline in my new to me 28 thou 2011 frontier SV V-6 4wd + netted 3 mpgs or so, used the 75-90 in the dana-nissan rear as recommended by dana, a real synthetic 75-90 on danas site not the 75-140 OE syrup which was semi-syn + just as costly. the redline MT-90 shifts so much better in my traded 200 thou jetta + now my 2001 audi TT, there IS a difference beside price + longevity IMO!!
 
The price difference isn't THAT great. Because I do it every 100K miles (so, twice) on my Tacoma, I use synthetic. You can catch it on sale.
 
Originally Posted by ragtoplvr
i had a 92 dodge Dakota v6 i put in a limited slip carrier. put in stay lube syn and immediately got 20 miles per tank. that continued for the next 100k. that was huge because it had a tiny tank. i went from needing to fuel at 150 pulling the boat to fuel at a 160 and 200 empty to 220 miles. i could pull the boat down to the lake and fish and back on one tank.after that. Just barely could not make it before..

rod
Seriously? Installing synthetic gear lube upped your mileage by 20 miles per tank?
 
Originally Posted by 2015_PSD
Seriously? Installing synthetic gear lube upped your mileage by 20 miles per tank?

I think that is not possible, especially considering the two lubricants may very well have chemically identical base stocks.
 
Originally Posted by kschachn
Originally Posted by 2015_PSD
Seriously? Installing synthetic gear lube upped your mileage by 20 miles per tank?

I think that is not possible, especially considering the two lubricants may very well have chemically identical base stocks.
From point of view, it is not possible even if they have different base stocks unless, of course, the viscosity changed from xW-600 to xW-90.
 
From what I have read on the topic, here is my understanding of conventional vs synthetic:

-- From a strictly "base stock" perspective, synthetic oil does not lubricate better than conventional. If there is an improvement in lubrication (more MPGs, more power, cooler running temperatures or something else), it's the additive package that makes the finished product a better lubricant. Synthetic oils being premium products, they often have better additive packages -- this includes improved detergent and dispersant package, so synthetics tend to keep engines cleaner, and they can clean up dirty engines quicker than doing more frequent changes with conventional.
-- Under equal operating conditions, synthetic oil lasts longer because it's better at tolerating high heat and shear, and generall resists breakdown better than conventional over time.
-- With the same viscosity, synthetic flows better at very low temperatures and thins less at very high temperatures (viscosity stable).

Modern conventional oils are excellent oils and I won't fault anyone for running conventional if it meets the manufacturer's requirements. But considering the small price difference, I think it is better to run synthetic. And when name-brand synthetic motor oil can be had cheaper (after rebate) than conventional, it is a 100% no-brainer decision for me.
 
The MPG benefit with synthetic would come particularly when the oil is cold as the synthetic will be much thinner than the mineral.

At 0 Deg C an 80W90 mineral is typically 2500 cSt. vs 750 cSt for a synthetic 75W90. If you happen to do a lot of short commutes and the oil rarely gets hot that will increase the mpg benefit of using synthetic.

I do a daily short commute all year round on my motorcycle and after changing to synthetic in both gearbox and final drive there was a vast reduction in oil drag felt by spinning the rear wheel by hand both before the ride and after.
 
I don't get why a lot of rear end rebuilders recommend conventional over synthetic. I get using conventional for a short break-in for cost reasons. I followed the instructions of my rear end builder, but now a year or more out, i'm thinking of syn.

For towing i'm running the 140 wt.
 
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Originally Posted by spasm3
I don't get why a lot of rear end rebuilders recommend conventional over synthetic. I get using conventional for a short break-in for cost reasons. I followed the instructions of my rear end builder, but now a year or more out, i'm thinking of syn.

For towing i'm running the 140 wt.



I'm no rear gear oil expert by any means
But I read a couple of months ago on a 4x4 forum of a guy who builds rear ends. He recommends conventional gear oil over synthetic for the greater shock load that conventional has over synthetic. Maybe that's true
 
Originally Posted by kstanf150
Originally Posted by spasm3
I don't get why a lot of rear end rebuilders recommend conventional over synthetic. I get using conventional for a short break-in for cost reasons. I followed the instructions of my rear end builder, but now a year or more out, i'm thinking of syn.

For towing i'm running the 140 wt.



I'm no rear gear oil expert by any means
But I read a couple of months ago on a 4x4 forum of a guy who builds rear ends. He recommends conventional gear oil over synthetic for the greater shock load that conventional has over synthetic. Maybe that's true


What exactly is shock load and how is it measured? Is this something speculative due to thinking conventional is thicker? I've heard that kind of thing, too, but nobody has ever ponied up with a measurement or even a convincing definition. I'm not saying not true. Just curious.
 
Here's what spicer gear has to say

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Originally Posted by kstanf150
Here's what spicer gear has to say


So I get shock load as it applies to the gears themselves. I should have clarified...how do you measure shock load of an oil? I take it to mean that the mechanic thinks the conventional gear oil can absorb or protect those parts against shock load better than a synthetic gear oil. How would the capacity of that oil for this be measured?

I'm skeptical that the same weight oil in a conventional vs synthetic can make a difference in those cases where the shock load on the gears was severe enough to cause a failure. I'm not being difficult. I've been skeptical of things before that turned out to be entirely correct.
 
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I'd love to know what exactly load shock protection in a gear means myself, I assume and we all know what that means
But I assume conventional gear oil not being as slick as synthetic may leave a thicker film of oil on the gears to cushion the gears as they mesh together. Just a thought
 
Originally Posted by grachik
If my 2000 F150 is used as a passenger vehicle only, is there a huge benefit to use synthetic lube in the differential?

Not a big advantage to me. The differential will out last the truck no matter which one you use.
 
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