Using Second Gear Down Long Hill

[Pitter]

This has been discussed before and I apologise but I've forgot and can't find the thread. Is using engine breaking (such as it is with the automatic) on a long downhill stretch deletirious to the engine in any way (though applying the brake when it reaches 3500 RPM or so)?

 

[cxha]

Sport mode will keep you in a lower gear to help maintain speed on downhill inclines.

 

[paris1]

No it won't. I use 3500 rpm as the limit in such situations. However Skyactiv G engines don't provide a whole lot of engine braking because of the valve overlap they use.

 

[madar]

I throw it into second occasionally to come down an 8 percent grade. Not terribly effective, does keep it from running away some. I limit engine speed to 2500 rpm so yeah, to try to keep to the 25 mph limit, there is some braking.

 

[HyFlyer]

Only thing officially in the Mazda owners manual I see under "driving tips" "descending steep grades" is ...

Descending steep grades


When descending a steep grade, shift to lower gears, depending on load weight and grade steepness. Descend slowly, using the brakes only occasionally to prevent them from overheating.

The owners manual doesn't specify staying under any certain rpm. I see you try staying below 3500 rpm while another poster stays below 2500 rpm. I'm happy with anything below redline. Of course, the higher the rpm, the more compression braking effect you will have.

I regularly use manual mode and downshift using compression braking on my 2.2 diesel for downgrades, exit ramps, slowed/stopped traffic on the highway ahead, etc. and it's fairly effective with 14.x:1 compression ratio.

I'm bot saying I'm right and others are wrong or my way is better. It works for me and I keep vehicles a long time with hundreds of thousands of miles with no power train problems. Some folks would say they'd rather buy brake pads than engines or transmissions or clutches. That's fine. Life's full of choices .

And I can't pass up an opportunity to say once again .... Diesel for the win! ... The 2.2 diesel is just a fantastic match for the cx5 .

 

[Pitter]

As to your last comment about engines vs. brake pads that is my original question.

 

[PatrickGSR94]

We vacationed last year in the Smoky Mountains with some very steep, narrow winding roads to get to our cabin. I found manual mode to be quite helpful for both going up and coming back down the mountain. When going up I found the Skyactiv 6 speed would often try to upshift too early, then would end up lugging the engine on the next hill such that I had to nearly floor it to make it downshift again. In manual mode I could just hold it in the lower gear and the engine ended up not having to work as hard. Then of course coming back down I could use at least some engine braking and not have to ride the brakes quite as much as I would have otherwise.

 

[ColtX-5]

The engine and trans are lubricated and water cooled. The brakes are just air cooled. The engine and trans are safe up to the redline (6250?). I find my engine gives plenty of engine braking on the mountain roads around Chattavegas and do it regularly. Outside of fuel mileage mode, it becomes a 13:1 compression ratio hot rod engine.

Fear not, but respect the redline.