WDBEA30D

My 1987 300E runs about 3500 rpm in top gear at 80 mph and about 3800 rpm at 90. 60 mph in 4th gear the car is already turning around 2500 rpm. When I move the gear selector into "3" the car downshifts, so I know that in "D" it IS shifting into 4th.

Is it supposed to be this way? If so, it seems to me that the transmission is geared very poorly for highway driving--especially for a Mercedes or any other "autobahn" car. BMW's, Lexuses and other Mercedes I have owned/driven would usually run somewhere in the range of 2500 rpm at 80 mph, which is much more relaxed.

This bothers me so much that when cruising down the highway at a rather raucous, high rpm, I am incessantly waiting for the car to upshift--but of course that can't happen because apparently the car is already in its highest gear.

It seems to me that wear on the engine and related parts would be dramatically increased under these circumstances, not to mention the negative effect on highway fuel economy.

RogerJones

That's consistent with my two M103 engines (max. revs 6200). Although the noise pitch is higher than with the M104 in my Coupé (max. revs 6400), I can't say that I find the level that much higher (even with the Turbo's stainless-steel exhaust system), although the M104 is a distinctly smoother engine all round. I nevertheless like the M103; having had the head gaskets fixed on both of them, I'm looking forward to many further years of enjoyment.

From a UK gallon, I get 24 miles out of the Turbo, 25 from the W126 and 27+ from the Coupé; 1 UK gallon = 1.2 US gallons; figures are long-term averages. A UK gallon of Shell V-Power (99 RON) is now costing me £4.63 = $9.25.

shdoug

$9.25?! I would have to walk...

Yes, that's the correct RPM. Mine is the same.

RBYCC

The 4 speed auto transmission in the early W124 with the M103 was not an overdrive unit.
Fourth gear ratio is 1.0.
What you experience in more modern vehicles is an overdrive gear with a numerical ratio of less then 1.0.

In fourth gear with tires of the same diameter as stock, you should see 23.3 mph per every 1000 rpm's.

60MPH / 23.3 = 2575 RPM.
80MPH / 23.3 = 3433 RPM
90MPH / 23.3 = 3862 RPM

So your speedometer / tach are reading correctly.

Top speed is reached around 6000 RPM @ about 141MPH.
Not too shabby for its time.

Properly cared for the M103 will outlive about all newer engines that operate at lower rpm's....

Nothing like cast iron simplicity !!!

Wadster

You know what's even more interesting? Even at those "high" rpm's (relative to other cars), my 300E 2.8 still got the same if not better mileage during freeway cruising as other overdrive equipped makes. As comparison, I had a GM rental car turning about 2K rpms @ 70 mph.

neanderthal

makes for much better freeway driving if you ask me. its already in the zone if you want to pass. no need for a downshift

and relatively thrifty at those rpms to boot. although i think thats more aerodynamics than anything else.

WDBEA30D

Thanks so much all for your quick responses! It's very reassuring to know that nothing is wrong with my car (at least with respect to my question!).

RBYCC, the rpms you calculated have got to be exactly the same as what I've noticed driving my car--in fact, I got a chance to validate the speed at 3862 rpm just this afternoon!

I still think Mercedes could have done better with a 5-speed auto (I know it didn't appear in the E until 1997), or a numerically lower 4th gear ratio--overdrive. Even so, you are right, the engine is incredibly smooth. I have an exhaust leak (will get it welded soon), so the louder exhaust sound might be calling my attention to the revs on the highway more that normally expected.

So did the 1992-1995 400E/E420 and 1992-1994 500E/E500 have the same transmission? If so, those must be especially durable, free-revving V-8's!

Any suggestions what kind of basic preventative maintenance is recommended to keep the engine in the best running condition? The car currently has just over 180K on it (60K on the tranny I am told), and I'm only driving it for as long as it takes me to save for a somewhat newer BMW 740 or Lexus LS 400 (no frowns please!). Obviously spending a lot of money on this car is going to inhibit me saving for the next car, but I don't want to blow up this car in the meantime either.

Certainly regular oil changes--does it make a difference to use synthetic? Coolant change? I heard leaving coolant in for a long time (and not using Mercedes coolant) can lead to blown heads/head gaskets. I've had the car less than a month, but I drive A LOT of miles. If it makes it to 200-220K, that ought to buy me enough time.

Again, thanks all.

PaulX608

The transmission ratios on the v8s are the same, but the final drive ratio is different. Your '87 300E has a 3.07:1 final drive ratio, my '93 400E has a 2.24:1 final. So, the v8s turn less revs for a given speed. I spend 52 miles a day with my cruise set at 80 turning just about 2500 rpm. I get around 23 or 24 mpg. Not bad for a 275 hp v8 sedan.

Eliot

The 7.225 five speed auto was first offered in the early nineties on the W124 chassis. I was corrected on that point a few months ago by someone who had it on their coupe. No idea on the reasoning but they just never offered it in America. The fifth gear is reportedly fragile and will give out before the rest of the assembly.

The V-8s have lower gearings. The E500 was offered in 2.82, the E420 in 2.65 (Europe) and in 2.24 (North America.) Brabus used the lower geared 420s as the basic of their six and seven liter v8 flagships.

Wadster

What exactly is that?

Untertürkheim

I thought the 87-93 300D (and 2.5 Turbo) had a 2.65 rear axle raito.

RogerJones

"Any suggestions what kind of basic preventative maintenance is recommended to keep the engine in the best running condition?"

Frequent oil changes, sticking to the oil previously used (but see below). I heed the advice of one of the UK's leading motoring journalists:

http://www.honestjohn.co.uk/faq/faq.htm?id=13

I switched my Coupé to Mobil 1 at 20k (now 58k); the Turbo has always run on fully synth (now 176k). The W126 was run on semi-synth until 136k; having had the head gasket done, I then re-read and reconsidered all the vast amount of information and advice I had gathered about oil, and decided to take a risk by switching to Mobil 1, in spite of some contrary opinions but in the light of one very well informed source who said that he had never encountered any problems switching to fully synth on the many high-mileage MBs on which he had worked. I've done a further 5k now and can detect no problems and not the slightest leak. I accept the argument that fully synth is simply a better lubricant. I am increasingly sceptical about some of the reports you see, such as "my engine started leaking all over the place when the oil was changed to fully synth".

Otherwise, I'd keep changing all fluids on, or ahead of, the handbook schedule. If you're doing plenty of miles, you're doing the car the best favour it could wish for.

Check out Irv Gordon's tips:

http://www.honestjohn.co.uk/faq/faq.htm?id=34

from his experience with his 2,000,000-mile Volvo.

PaulX608

Yes, that's right. The 2.65 was used on the following models:

124.032 1993 300E
124.052 1993 300CE
124.066 1994-1995 E320 Cabriolet
124.092 1994-1995 E320 Wagon
124.128 1990-1993 300D 2.5 Turbo
124.133 1986-1987 300D Turbo


The 3.07 was used on:

124.030 1986-1992 300E
124.050 1988-1989 300CE
124.193 1986-1987 300TD Turbo
124.230 1990-1992 300E 4MATIC

RBYCC

The early 260E and 300TE gasoline cars used a lower 3.27:1 rear which if used in the 3.0L cars becomes a performance gear which gives you most bang for your buck to increase acceleration !

Jackd

,.....most bang for your buck to increase acceleration ....

The word ""acceleration""" and """260E""" in the same sentence??????????


Wow!

Komet

I was thinking of putting a 2.65 diff. from a 1987 300D turbo in my 300E inorder to lower high speed rpms to increase fuel efficiency. What do you all think ?? I do mostly high speed (75-85mph) highway driving. Thanks for you input.

Eliot

You might gain 2-4 mpg. Take offs will be slower.

neanderthal

read, follow, apply all the thinkology stated in the fuel efficiency threads.

*get rid of excess weight
*get a tuneup and oil change
*keep windows and sunroof closed
*minimal use of AC
*slightly taller tires (205/65-15 vs the OE 195/65-15)
*slight increase in air pressure, but not more than the stated max on the sidewall
*coast to stops/ maintain that braking space. this is a huge one, and i employ it to great effect in los angeles traffic. acceleration kills fuel efficiency.
*accelerate to cruising speed briskly but not drag racing.
*keep a light foot on the gas, let the momentum of the car drive it.


by following these simple tips i eked out a 25mpg avg at 75 mph avg from parker, colorado to los angeles. mind you, i was doing 100 plus in some areas. i wasnt doing forty and drafting a big rig.

my car was originally rated as 19 city 23 freeway. thats nearly a 10% increase vs the EPA freeway rating. at a 75mph avg. thats the kicker.

ps, if you do the diff swap, at least get the 1st gear start mod to increase your pick up.

RogerJones

Excellent set of tips. I would only say that I saw little impact on fuel consumption from switching off the A/C in both my first E320 Coupé and the VW Golf VR6 I had at the time. I'd much rather leave the A/C on because all the advice I've seen online and heard from the A/C fitters is of the "use it or lose it" variety. I noted that the A/C button was off by default on my first Coupé and on by default on my current one, and I take it that MB did that to reduce the chances of "lose it".

Smooth driving is important not only for fuel economy but for passenger comfort and safety. I see so many drivers wearing out their brakes for want of keeping safely back from what is ahead of them and anticipating when traffic lights will change. Smooth driving doesn't mean slow driving.

When you're paying what we Brits pay for fuel, you do worry about these things.

Oh, and I wouldn't use tyre pressures other than those that are correct for the car.

RBYCC

Roger

I note that you have a 300E Twin Turbo.
Is it a TurboTechnics or Mosselman install?

Just completed a TurboTechnics install with some modern modifications and curious about your comments on your vehicle.
Thanks

Ed A.

Eliot

As no ones mentioned it yet Turbo Charging also improves mileage.

nsur-nvst

This was very helpful info...1990 300E at 3800+ RPM at 88-90MPH. I thought was high but seems all is in line as normal.

THANKS!