SRT Hellcat Forum banner
  • Hey Everyone! Enter your ride HERE to be a part of this months Ride of the Month Challenge!
1 - 15 of 15 Posts

·
Registered
Challenger SRT Hellcat
Joined
·
97 Posts
Discussion Starter · #1 ·
Hey guys, had a friend throw me a couple pouches of these when talking about changing my diff oil. I think recommended is 75w-90 if I'm not mistaken, but nothing wrong with 80w-90 is there? I live in FL if the temp makes a difference. If Good, I'm just gonna get some slip lock and get it done.

Thanks
 

·
Registered
Challenger SRT Hellcat
Joined
·
753 Posts
I did mine today ,valvoline 75/90 with the additives in it already. Im not sure how long i have to drive it around, but I drove it for 5 miles and did some figure 8s to work it in. I still heard some grouns from the rear on sharp turns so I'm hoping it will go away soon. Only 28k on it and by no means an abused car.
 

·
Registered
2020 Challenger Hellraisin Scat Pack.
Joined
·
2,564 Posts
Hey guys, had a friend throw me a couple pouches of these when talking about changing my diff oil. I think recommended is 75w-90 if I'm not mistaken, but nothing wrong with 80w-90 is there? I live in FL if the temp makes a difference. If Good, I'm just gonna get some slip lock and get it done.

Thanks
If the factory had thought there was nothing wrong with 80w-90 it would have listed this as an acceptable fluid.

My advice is use the fluid recommended by the factory.
 

·
DRIVESRT.COM
Challenger SRT Hellcat
Joined
·
4,803 Posts
Hey guys, had a friend throw me a couple pouches of these when talking about changing my diff oil. I think recommended is 75w-90 if I'm not mistaken, but nothing wrong with 80w-90 is there? I live in FL if the temp makes a difference. If Good, I'm just gonna get some slip lock and get it done.

Thanks
Amsoil 75W-90 with the 4oz Mopar Friction modifier is a good choice. Mopar was running a special blend 75W-85 from factory.

 

·
Registered
Challenger SRT 392
Joined
·
7,160 Posts
I'd run that 80W-90, that's good stuff and many guys run the 110 or even 140W.

Sent from my SM-N960U using Tapatalk
 
  • Like
Reactions: Glenn_B

·
Registered
Charger SRT 392
Joined
·
268 Posts
I wouldn't bother risking it, it's cheap enough to get the 75w90 with a tube of slip lock.
 

·
DRIVESRT.COM
Challenger SRT Hellcat
Joined
·
4,803 Posts
But do they run the Amsoil 110 or 140? Oi was finkin' of doing that.
Amsoil does have a 110 and 140. We've used Amsoil 75W-140 in Vipers with the Mopar 4oz Friction Modifier before and I have also used it in the Hellcat. It runs thicker when compared to the 75W-90 at the same temperatures.

amsoil.png
 

·
Registered
Charger SRT Hellcat
Joined
·
1,129 Posts
Decisions, decisions...........I need to do mine in the next month or two.
 

·
Registered
2020 Challenger Hellraisin Scat Pack.
Joined
·
2,564 Posts
Lol so kind of split opinions.
Yes, you ask 6 guys what vital fluid to run and you get 7 answers.

My recommendation is stick with the what the factory recommends. The factory tests cars in a variety of climate conditions from the heat of summer in the southwest to sub zero temperatures in Alaska or perhaps in northern Canada.

The factory is the only real authority on what fluid to use.

As an aside, "thicker" ain't always better. A good example of this in with the 5-speed manual that was shipped in the "new" (circa 1996) Mustangs used ATF. Some owners felt this was too "thin" and used -- or worse just recommended to other owners to use -- 75w-90 gear oil (or whatever viscosity of gear oil the other manuals used).

Turns out this was too thick to properly lube the needle bearings that supported some shafts and premature transmission failure was the result.

OTOH, I ran the factory fluid (ATF) and drove my car to 150K miles with no signs of any transmission issues.
 

·
DRIVESRT.COM
Challenger SRT Hellcat
Joined
·
4,803 Posts
Yes, you ask 6 guys what vital fluid to run and you get 7 answers.

My recommendation is stick with the what the factory recommends. The factory tests cars in a variety of climate conditions from the heat of summer in the southwest to sub zero temperatures in Alaska or perhaps in northern Canada.

The factory is the only real authority on what fluid to use.

As an aside, "thicker" ain't always better. A good example of this in with the 5-speed manual that was shipped in the "new" (circa 1996) Mustangs used ATF. Some owners felt this was too "thin" and used -- or worse just recommended to other owners to use -- 75w-90 gear oil (or whatever viscosity of gear oil the other manuals used).

Turns out this was too thick to properly lube the needle bearings that supported some shafts and premature transmission failure was the result.

OTOH, I ran the factory fluid (ATF) and drove my car to 150K miles with no signs of any transmission issues.
Hellcats are fine with the factory 75W-85 or 75W-90 that Amsoil/similar vendor has. However, there are better options than the factory fill when it comes to temperature resistance and oil sheer; especially as people drive Hellcats more spirited (e.g. burnouts) or race them and the rear differential gets very hot. For example, the 75W-85 has a flash point of 190 C (374 F) and a VI of 83 vs. Amsoil 75W-90 that has a flash point of 206 C (406 F) and a VI of 166. Similarly, we use a DOT 4 rather than the recommended factory fill DOT 3 for the brake fluid so it doesn't boil off during racing.
 

·
Registered
Joined
·
3,499 Posts
Turns out this was too thick to properly lube the needle bearings that supported some shafts and premature transmission failure was the result.
THIS is my main concern with using higher-viscosity oils. Any increase in viscosity moves it closer to acting like grease, instead of oil.
For big rigs, the ring gears turn slowly enough that the oil isn't going to be all pasted to the outer circumference of the case, but for something like the Hellcat, with its higher revs-per-mile, not to mention higher-revs-per minute just due to faster driving, I would also be concerned with oil starvation, and at very high speeds, with oil starvation from between the actual gear teeth.

The less viscous a fluid is, the more likely it is that it will find its way to where it's needed at higher RPM. The more viscous it is, once it is flung away from a moving surface, it is harder for it to make its way back to said moving surface.

If I were really going after high-speed records, I may want to pump the oil into the desired locations, most especially the roller bearings in the rear rend.

Some big rig rear ends actually have pumps to oil the spider gears to ward off failure from overheating.

I wonder if slightly overfilling one's trans or rear end is a cheap guard against such overheating or starvation. As with many things, a balance must be struck, and constantly forcing the gears to slog through "waist deep" oil does nothing to reduce heat generation or increase fuel mileage.

It makes me wonder how Hewland and other such racing boxes are oiled? Gun-drilled main shafts? Spray? Splash?

What reduces oil longevity other than particulates and such in the oil from its environs is peak temperatures. Oil will last a lot longer if its peak temperature never exceeds, for example, 90 degrees. However, as stress rises from temperature and interactions between the moving parts, oil can be heated momentarily at the contact point to far beyond its recommended operating temperature, and this is what causes thermal breakdown, as a majority of the oil volume is eventually exposed to whatever mechanical interface elevates the temperature above the point of damage to the makeup of the oil itself.

If your oil cooler has a thermostat, I see no harm in having an oil cooler that is two or three times the capacity of the stocker. The thermostat will keep the oil at a temperature close to a desirable range, and the larger capacity will ensure that the thermostat spends less of its time open. Ideally, one's oil cooler would have a PROPORTIONAL thermostat, or TEV (Thermal Expansion Valve) like they use in air conditioning to meter refrigerant flow, so the oil coming back to the engine/trans/rearend/your slick hairstyle would always be at a temperature that precluded or reduced those "spot-coking" events.

I wonder if one were to remove the thermostat, if one exists, from the blower coolant circuit, and run a massive amount of cooling for the coolant of the blower bricks, would one ever run into an environment where that was somehow undesirable? The blower seems to heat the intake air up from conduction from the engine and thrashing of the (even when idle) supercharger lobes to the point where I think you would be hard-pressed to find a cold enough situation where it was a net negative.

If one were truly fanatical and rich, one could build a drag strip that was heated, and run races at sub-zero temperatures, to measure the benefits of extra cooling.

Especially with the ECM pulling timing to allay detonation concerns, and dumping in more fuel for the selfsame problem, why would a nice, cool intake charge be a negative? I guess fuel droplet atomization/dissolution would be less effective the colder the intake air and fuel itself.
 

·
Registered
Joined
·
3,499 Posts
Hellcats are fine with the factory 75W-85 or 75W-90 that Amsoil/similar vendor has. However, there are better options than the factory fill when it comes to temperature resistance and oil sheer; especially as people drive Hellcats more spirited (e.g. burnouts) or race them and the rear differential gets very hot. For example, the 75W-85 has a flash point of 190 C (374 F) and a VI of 83 vs. Amsoil 75W-90 that has a flash point of 206 C (406 F) and a VI of 166. Similarly, we use a DOT 4 rather than the recommended factory fill DOT 3 for the brake fluid so it doesn't boil off during racing.
So, flash point is the temperature at which the oil will combine with any available atmospheric oxygen. If you have a higher flash point, that means fewer micro-coking-ish events where the oil is locally elevated above its flash point AND has access to oxygen. If one were to fill one's gearbox with nitrogen instead of regular ol' air, one would experience less oil deterioration, I imagine, but how to KEEP it so only nitrogen is in there. That is the thing. Especially if one were to do that with one's engine crankcase.
 
1 - 15 of 15 Posts
Top