mbluver111

I know this is a newbie question, but I just used regular (Drive) and rarely change gears since I don't drive near uphill or downhill roads. Can you guys explain to me when to use the gears of (1,2,3,4,5,6)? Recently I took my parents to go somewhere and there was an uphill road, they told me to switch to D2(which is the 2nd gear), but it sounded rough, so I had to switch to 3rd gear which was more smoother. Once we got onto the regular road I switched back to regular drive. Even though I switched to 2nd gear for about 5 seconds and it sounded rough, would it cause damage to anything? Also let me know on when to use these gears when needed. Thanks in advance.

listerone

I know basically nothing about this kind of thing but I think it's connected with RPMs.You don't want to surpass redline so as to not damage the engine but,OTOH,there's an RPM range that's best suited to things like passing,climbing steep hills,etc.I don't use the paddle shifters on my BT but I think I have a trip to the Rockies planned in which case it would probably be to my benefit to learn how to use them both climbing and decending.

telemakhos

Unless you want more sporty performance and like to change gears yourself you'll be fine just leaving the automatic do its thing. It will choose the correct gear based on load and and speed.

As for changing gears yourself, you can get more power by dropping down gears at a given vehicle speed (don't go over the redline) since the engine RPMs will go up which corresponds to more HP. Look at the HP and torque curves vs RPM graphs.

I down (paddle) shift sometimes when merging onto a highway when I want more "oomph" but that is about it. On my old E class when going up a steep grade I found that the tranny choose too high a gear in one particular case so I dropped down a gear.

Cavu

When you select a gear with the shifter, like D2, you're telling the engine to not shift any higher than 2nd gear. If you were in drive and did a manual downshift then you must have been in 3rd gear at the time. The engine would have sounded louder because the RPMs increased, but I don't think it would get anywhere near redline.
The shifting is handy on some roads when you want to select a max gear so you can climb a hill easier or use the engine compression to slow down.

ttoE550

You probably did not hurt anything. Once the engine is warmed up, the electronics will prevent you from doing any damage to your engine while under ACCELERATION. It will automatically shift before redlining (overrevving). It is not a good idea to run the engine at high RPM before it has warmed up.

Remember this is a 7-gear transmission. Someone used to a 5-gear might say 2nd gear is best, when in fact 3rd gear might be best on this car.

The potential danger is in using the engine compression to slow down. Under acceleration, the electronics can cut spark plug firing, etc., to prevent overrevving. Under DECELERATION, however, it is the weight/momentum of the car that can cause revving past the redline and engine damage. Maybe in this car the electronics would automatically shift the transmission, but this is not something I'd want to test!

mbluver111

Good thing I don't drive near steep hills. What is redlining and RPM? And how would you know if you are near redlining? Just wanted to know. Thanks

ttoE550

RPM = revolutions per minute, "how fast stuff is moving in the engine" An engine is designed with a certain maximum RPM, called the redline. Beyond the redline, the engine parts are moving too fast and all sorts of bad things can happen to the engine. If you look at your tachometer, there is an area marked in red - that is the redline area. I believe it is about 7500 RPM, but I don't remember for sure. As a side note, Formula 1 racing cars use V8 engines that are limited to about 18,000 RPM but could do about 23,000 RPM.

If you keep your car in auto mode, you needn't ever be concerned about redlining. The car will handle that. It is only when you put the car in a low gear on a steep downhill grade that you MIGHT need to worry about it - I do not know whether the electronics would prevent going past the redline by shifting. I suspect it would, but I don't want to blow my engine trying to prove it.

With a manual transmission, you can damage your engine by downshifting to too low of a gear.

mbluver111

Thanks for the helpful info guys. I just like to keep it simple and drive automatic. It's been about a month since I got this beautiful piece of art. After two weeks into buying it, one of my friends who is very knowledgable about cars drove it. He knew all about shifting gears so I allowed him to drive the car for about 5 minutes. Since he knew how to use the gears, we went on the freeway and he started to shift to (gear 2) I believe which made the car faster. I was thinking to myself, I can't believe I'm letting this guy drive it, even for a couple of minutes. What do you guys think about shifting to gear 2 on the freeway to accelerate even when the road didn't have any up or downhills.

ttoE550

Well, the manual says that you should keep the RPM below a certain level for the first xxxx miles. I forget the numbers. Something like below 4000 RPM for the first 1000 miles, but I will leave it to someone else to verify the correct numbers. Many knowledgeable people say this isn't necessary, and the dealers certainly do not discourage violating this on test drives.

Aside from that, it is very unlikely you will harm your car. First, the car is designed to be operated in the ranges permitted by the electronics. Second, the electronics will generally keep you from doing anything accidentally that would harm the engine, etc.

Actually, there might be some benefit to occasionally running an engine hard (the Italian tuneup):

http://en.wikipedia.org/wiki/Italian_tuneup

Normally one would not do this all the time. Your gas mileage would suffer greatly (very greatly) and would cause some components to wear in less time than usual.

evanswan

common sence.