chieftam

A new GL320CDI owner here with a question. Just got my GL320 after years of Ford Powerstroke diesels. My Powerstrokes would loaf along at about 1750 rpm at 70 mph with 3.73 gears. With a seven speed auto, two overdrives and 3.45 gears, I was suprised to find my MB running at 2000 rpm at 65 mph. I can't seem to find the ratios for the overdrives, but it seems like this is a little high. Is this the normal rpm range? An online review by Edmunds, I think, said they were hitting 2000 rpm at 65 in 6th gear, and it dropped even lower in 7th. Only 325 miles so far, but am I not getting into 7th? Other than that, love the vehicle. Thanks for the help.

scottybdiving

I too came to the GL 320 after many years driving a Powerstroke. Actually, my wife drives the GL, but I have noticed that it runs at considerably higher RPM's than the Powerstrokes or my current Duramax. The idea of getting that much torque and HP from a 3.0L V6 is still mind blowing to me. I think it has to work a little harder to achieve it than what we are used to.

StevethePilot

One thing I do sometimes (well, a lot) is hit the "up-shift" button (for some steering wheels, it's one side to up shift, the other to down shift - on mine it's the outsides of the buttons to up shift, the insides to down shift) while the cruise control is on and I'll usually drop around 100 RPMs (depending on speed). It's like it's not shifting into 7th as soon as I'd like. I thought it was just the GL but the same thing happened on my loaner (the C).

That said, at 65 I'm usually out of gears (it's already in 7th). I think maybe it really is just that the engine has to work a little harder to produce that much power from so small a powerplant.

Comfy_Couch

Using the steering wheel mounted shift buttons, you can switch to manual mode just to check what gear it's in.

lkchris

Big difference indeed between 3.0 l and 7.3 l.

mbslk350

My GL320 also runs 2000 rpm at 65 mph.

For comparison, my 3.5L V6 gas-powered SLK350 with the 7-speed tranny runs 2200 rpm at 65 mph.

And my 3.2L V6 gas-powered SLK320 with the 5-speed tranny runs about 2500 rpm at 65 mph.

So the diesel engine revs the lowest of the three. But, like you, I was expecting even lower revs from a diesel engine mated to a 7-speed tranny.

TV550

maybe the engines have to reve that high to keep the turbos going so you can have instant on demand torque?

chieftam

Thanks for all the information, I guess my vehicle is on par with everyone elses then. I was just concerned as I am usually in the 80 mph range when I travel, although I haven't hit that speed yet due to so few miles on the vehicle, but was just concerned that it might be running 3000 rpm or more at that range, and for 1000 mile trips, it just seemed like alot. I will try using the manual shifters next time I'm on the highway.

dieseldel

The rpm seems about right for the size of the engine.
My Cummins turns 2250 at 75mph, but its much larger and heavier.
Turbo speed only affected by the exhaust volume/speed, not the engine rpm.

It all seems right to me.
May you have many enjoyable miles.

Danno4x4

According to the specifications for the motor, the 3.0 CDI in the GL puts out 398 lb-ft @ 1,600 - 2,800 rpm, so at 2000 RPM that puts it right in the middle of the fat torque curve, which is really the most efficient spot in the engine's operating range, so it makes sense.

StevethePilot

And again, the award for "Most Knowledgeable About His Car" goes to Danno!

oinick

It takes a little getting used to, but the transmission does a really great job of keeping the motor in the fat part of the torque curve. Even after a year and a half of driving it, sometimes I still think it's not shifting into the higher gears as it should.

But you've got to love the instantly available torque for passing and towing at highway speeds.