dino or synthetic for diffs?
- Thread starter cowtipper
- Start date
- Status
I don't know about conventional lubes running cooler, but yes heat is an issue that can lead to lubricant breakdown. Synthetics will stand up to heat better and provide better cold weather performance. You can usually run them longer than conventionals as well.
Hi,
Kurt - Typically a synthetic gear oil will run cooler than a mineral oil will when similar viscosities are compared
They also provide better thermal and oxidation stability!
If the differential has been on a mineral oil for a long period it is possible seal seepage may occur on conversion to a synthetic
It is important to use a gear oil that is specified for the application
IME excessive heat has never been an issue. Above 120C (250F) creates unwelcome oxidation - most diffs IME operate from 75C to around 105C. Synthetic gear oils work very well in low ambient and operating temperatures too of course
Kurt - Typically a synthetic gear oil will run cooler than a mineral oil will when similar viscosities are compared
They also provide better thermal and oxidation stability!
If the differential has been on a mineral oil for a long period it is possible seal seepage may occur on conversion to a synthetic
It is important to use a gear oil that is specified for the application
IME excessive heat has never been an issue. Above 120C (250F) creates unwelcome oxidation - most diffs IME operate from 75C to around 105C. Synthetic gear oils work very well in low ambient and operating temperatures too of course
Being one of the most neglected sumps in the vehicle, a synthetic gear lube really is the only way to go in this kind of environment.
Originally Posted By: AzFireGuy79
Being one of the most neglected sumps in the vehicle, a synthetic gear lube really is the only way to go in this kind of environment.
+ one on that......
Being one of the most neglected sumps in the vehicle, a synthetic gear lube really is the only way to go in this kind of environment.
+ one on that......
Some limited slip diffs spec donot use synthetic because it allows the clutches to slip.
JHZR2
Staff member
The first thing I do when I get a new (to me ) MB diesel is put sun in the diff. I've seen the cleaning that it can do, and it is great enough to justify use...
Never had a leak on one yet either...
Never had a leak on one yet either...
I say synthetic. Compared with motor oil, you are changing that relatively often and it's simple to do. Since you are changing often and you have to buy ~5 qts, you save a lot buy purchasing less expensive oil that gives good protection.
Changing the diff oil can require new gasket and messy cover removal. You also do this much less frequently and you only purchase a small amount. Dino might be fine but you are saving much less by choosing dino in this application so why not spend the extra buck or two and know you have the best.
Changing the diff oil can require new gasket and messy cover removal. You also do this much less frequently and you only purchase a small amount. Dino might be fine but you are saving much less by choosing dino in this application so why not spend the extra buck or two and know you have the best.
In reality, I would bet most differentials live their entire lifetime with neglected oil changes and conventional fluids, and nobody ever knows the difference. Changing the fluid with any type and grade the manufacturer recommends is a step in the right direction. Synthetics probably don't make any appreciable difference in service lifetime or operating characteristics of most differentials. The ones that might run hot probably have a heatsink to offset the difference and keep the fluid properties in check. People will cite all sorts of technical stuff about the fluids, wild speculation, and over-thought rationality, and I'm no different, but in the end, synthetics probably just cost more and provide no tangible benefits other than to your psychological well-being.
Originally Posted By: Bob Woods
Some limited slip diffs spec donot use synthetic because it allows the clutches to slip.
i know that a common assumption but my GM car has a limited slip and only synthetic is recommended, so it was in my 2005 car. GM has been putting synthetic oil in rear differentials for more than 10 yrs. They started factory filling all trucks/suvs back in 1999.
mineral gear lubes are inefficient and have less heat resistance.
Some limited slip diffs spec donot use synthetic because it allows the clutches to slip.
i know that a common assumption but my GM car has a limited slip and only synthetic is recommended, so it was in my 2005 car. GM has been putting synthetic oil in rear differentials for more than 10 yrs. They started factory filling all trucks/suvs back in 1999.
mineral gear lubes are inefficient and have less heat resistance.
Syn oil is a really good choice for differentials since they are often ignored by most.
I have used everything from bulk no-name dino to Royal Purple and Mobil 1. I haven't really noticed any difference between dino/syn and cheap/expensive fluids. I think what is most important is changing it regularly (30-50K miles is a good rule of thumb for many diffs) and changing it when it gets contaminated with water or mud.
Personally, I have never experienced differential problems with any of my trucks. I tow smaller trailers with things like ATVs and do some light off roading.
Personally, I have never experienced differential problems with any of my trucks. I tow smaller trailers with things like ATVs and do some light off roading.
I know that putting synthetic Mobil 1 diff fluid in the rear diff of my 98 K1500 at 20,000 miles, didn't keep my pinion and carrier bearings from starting to fail at about 75,000 miles. This was on a truck that never towed anything bigger than a 5x10 utility trailer and never hauled anything heavy at all.
I run a conventional diff fluid now.
Wayne
I run a conventional diff fluid now.
Wayne
Synthetic diff fluid is spec'd by Nissan for my diff in the Frontier.
Originally Posted By: wtd
I know that putting synthetic Mobil 1 diff fluid in the rear diff of my 98 K1500 at 20,000 miles, didn't keep my pinion and carrier bearings from starting to fail at about 75,000 miles. This was on a truck that never towed anything bigger than a 5x10 utility trailer and never hauled anything heavy at all.
I run a conventional diff fluid now.
Wayne
My sons 91 Ranger has 350K with two diff oil changes. M1 75-90 and has never had a part replaced.
I know that putting synthetic Mobil 1 diff fluid in the rear diff of my 98 K1500 at 20,000 miles, didn't keep my pinion and carrier bearings from starting to fail at about 75,000 miles. This was on a truck that never towed anything bigger than a 5x10 utility trailer and never hauled anything heavy at all.
I run a conventional diff fluid now.
Wayne
My sons 91 Ranger has 350K with two diff oil changes. M1 75-90 and has never had a part replaced.
Last edited:
Originally Posted By: cowtipper
Which is better for diffs?I've heard that dino lubes run cooler,but is that better?I know synthetics hold up under heat better,so is heat really an issue at all?Thanx,Kurt
My opinion from what I have read is that if your car maker doesn't specify synthetic you don't need it, and if they do specify it, then that is what you should use. I think all 75W-90 lube is synthetic, and it is used to give better mileage when the lube is cold.
The best conventional 80w-90 gear lube that I have used is SWEPCO 203. I have not compared it to 75W-90 because it costs more than Amsoil SVG.
Which is better for diffs?I've heard that dino lubes run cooler,but is that better?I know synthetics hold up under heat better,so is heat really an issue at all?Thanx,Kurt
My opinion from what I have read is that if your car maker doesn't specify synthetic you don't need it, and if they do specify it, then that is what you should use. I think all 75W-90 lube is synthetic, and it is used to give better mileage when the lube is cold.
The best conventional 80w-90 gear lube that I have used is SWEPCO 203. I have not compared it to 75W-90 because it costs more than Amsoil SVG.
Just like there are many recipes to make a cake, there are just as many to make a synthetic gear lube. People tend to think because its synthetic, its all the same. No more true than all radial tires are the same.
Synthetic is just a term to define how its made, synthetic = engineered fluids
Synthetic is just a term to define how its made, synthetic = engineered fluids
Originally Posted By: meep
every dino diff that I have put synthetic in has rewarded me with a slight (0.5) mpg increase. Period.
97 legacy (front & rear)
97 pathfinder (rear -front had manual disconnects)
2008 cherokee (rear, 2wd)
How did you equalize all the other factors and isolate just the differential fluid as the source of the increase?
every dino diff that I have put synthetic in has rewarded me with a slight (0.5) mpg increase. Period.
97 legacy (front & rear)
97 pathfinder (rear -front had manual disconnects)
2008 cherokee (rear, 2wd)
How did you equalize all the other factors and isolate just the differential fluid as the source of the increase?
- Status