Engine revving going downhill

greetings!

i gotta a 2015 4x4 four door with 110k miles. automatic

everythings been great so far love this truck…

i just noticed this annoyance (dont know if its new or not)

when im coming down a big hill or a mountain, the engine rpm is fine.

then as the truck gains speed and im obliged to brake, the rpm rises significantly as if the truck is downshifting. This is very annoying as its unsolicited, the brakes are doing their job.. it strains the engine and wastes a ton of gas. Is this normal?

to avoid this i often just throw it in neutral and peacefully coast down. is this ok? I just had the trani fluid changed

 

It's normal. It's an engine braking feature to keep you from riding the brakes down long grades. I believe you can go from D to 4 back to D to override it when it's occurring.

 

Sounds fairly normal to me.
In any case it isn't hurting anything, if you aren't on the throttle and the engine RPM is above around 1300-1500 and coasting down the fuel injectors are turned off so it's not wasting fuel. It's called Decel Fuel Cut, it's a standard "feature" on all fuel injected engines.

Engine braking isn't gona hurt the engine either, big rigs and HD trucks do it all the time to save their brakes in fact most vehicles with a Tow/Haul mode will downshift (some quite aggressively) during braking when Tow/Haul mode is turned on to help slow down. Granted gas engines don't have near the engine braking as diesels but they still will help slow down.
I have a manual and downshift to engine brake all the time.

 

Yup, as has been said, engine braking doesn’t burn any more gas or hurt the engine a bit as long as you’re not redlining the thing. I noticed the same thing in a couple corollas and Camrys I’ve driven. Saves brake wear and is helpful in foul conditions as it creates the same braking force with less brake pressure, therefore more controlled and less chance of breaking traction. In addition to not having to heat up your brakes as much on long downhills.

 

Modern engines don't use fuel when coasting or engine braking.

It's called "fuel cut". Unlike a carb the ecu will send little to no fuel to the engine when there is no demand from the driver.

Using neutral is technically wrong and possibly dangerous.

 

It's normal.
Mine does it fairly regularly.
Although I think it does it mostly, or always, when braking. (I have an Auto).
I need to pay closer attention. Now I'm curious exactly if the brake switch plays a role.
Never thought about it until now.

 

Normal. It’s not necessarily wasting a ton of gas either. RPM is only one component of it, the other is how much load is on the engine.

 

Normal and a lot better than riding the brakes down a hill.

 

Because it is downshifting. Mine rarely does it because most of the time I proactively downshift manually before the truck does it. Just because it is an automatic doesn't mean you can't manually select the best gear to be in. Doesn't hurt a thing.