Daimler Chrysler stated in a news article, posted here somewhere in the forum, that it was safe to use regular unleaded on any DC car, even the high end models that were produced after a certain year.

I decided to try it out and I can tell you that the only differences I've noticed is how much I spend to fill up my car and that I get better gas mileage. Other than that, the car performs and runs the same.

 

Here is a lesson about octane all fluids have a vapor pressure point. Gas will ignite under compression and the lower the octane the lower the compression it will ignite. Most engines perform best with advanced timing just shy of ping (pre-ignition, of course higher octane will eliminate this ping at the advanced timing) High performance (high compression) engines need a slower burning gas as not to ignite to soon.

Ok, with the new technology in our microprocessor controlled engines if you put cheap gas lower octane in your tank the engine control system will automatically retard your timing to compensate for the lower octane to reduce ping (pre-ignition). Therefore your car will not be running at peak performance, you may not notice it in normal driving, but it will effect high rev performance and also gas mileage.

 

Guys, it is the long skinny peddle on the right.

I get about 18 in my auto, all city driving.

 

Thanks for the info...

 

Give me a clue - how are MB supposed to make manual transmissions change at a particular shift point - that would make it an auto.

The improvements in Auto transmissions have mostly been through locking up top and sometimes one below top - usually 4th and 5th.

I am surprised that Auto's could have better figures, on a manual all the gears are "locked" and the shift point will not make much difference on a consumption test.

 

In 'easy' driving the auto shifts very quick and runs at 1,500-1,800 RPM. That's the main reason why the consumption is lower, IMO. If I drive with AutoStick my consumption is appreciable higher because I let the engine turns higher than 2,000 RPM for sportier driving.

 

Just checked my mileage on a 330 mile trip and averaged 26.5 mph. Most of the trip included highway driving. Not too bad.

 

In 8,500 miles of driving my '04 6 speed. I've gotten a low of 22.0 mpg and a high of 31.5 mpg. My over all average has been 25.7 mpg. I use nothing but Hi-test.

 

25 to 30 depending on how much city driving I have to do.

 

This would make it the only auto that gets better gas mileage using an automatic transmission.

 

I think I can accept chxf's point that when not pushed the auto changes earlier than most manual drivers would, on a standard consumption test, details for UK test below, I would have to assume the driver has to accelerate at a particular rate.

The test is outlined in Directive 93/116/EC and provides results that are more representative of actual average on-road fuel consumption than previous tests. There are two parts: an urban and an extra-urban cycle. The cars tested have to be run-in and must have been driven for at least 1,800 miles (3,000 kilometers) before testing.

Urban Cycle:
The urban test cycle is carried out in a laboratory at an ambient temperature of 20oC to 30oC on a rolling road from a cold start, i.e. the engine has not run for several hours. The cycle consists of a series of accelerations, steady speeds, decelerations and idling. Maximum speed is 31 mph (50 km/h), average speed 12 mph (19 km/h) and the distance covered is 2.5 miles (4 km).

Extra-Urban Cycle:
This cycle is conducted immediately following the urban cycle and consists of roughly half steady-speed driving and the remainder accelerations, decelerations, and some idling. Maximum speed is 75 mph (120 km/h), average speed is 39 mph (63 km/h) and the distance covered is

4.3 miles (7 km). Combined Fuel Consumption Figure:
The combined figure presented is for the urban and extra-urban cycle together. It is therefore an average of the two parts of the test, weighted by the distances covered in each part.


edit - just found these UK figures, looks like the extra urban cycle makes the difference - ie when the box is locked.

second edit - shows how you can misread figures when you think you know what they should say, the urban section (town) is better on the AUTO!


Manual
Extra Urban Cycle 37.2 (7.6) mpg (l/100 km)
Urban Cycle 18.3 (15.4) mpg (l/100 km)
Combined Cycle 27.2 (10.4) mpg (l/100 km)

Auto
Extra Urban Cycle 36.7 (7.7) mpg (l/100 km)
Urban Cycle 19.8 (14.3) mpg (l/100 km)
Combined Cycle 28.0 (10.1) mpg (l/100 km)

 

I just got back from Tenn./N.C. and check this out, it varied from 21.5 - 22 mpg when I was "beating the heck out of it" in the mountains, to 29.5 to 33 mpg when cruising on the freeway, the car gets better mileage than the window stickers says, GREAT!

 

I filled up at the southern Virginia state line then drove exactly 300 highway miles and refilled, it took 9.7 gallons so it was getting a little over 30 mpg.

 

We only use our car for trips so we have been seeing about 33 mpg at 70 mph, but above 100 mph it drops drastically to 26 mpg. The car averaged 28 mpg on a 2K mi trip with probably 40% at 95 mph while we traveled through WY and MT.

 

I drive in L.A., mostly short trips, but also freeways up to 80 MPH. I like to punch it sometimes, to get on the freeway or pass a car. Under all conditions I average less than 20 MPG Premium. Disappointing. However, one of the reasons you but a sports car is to have some fun. This is not an economy car.

 

After 13,764 miles I am averaging 26.7 MPG. (I used 515.6 Gallons of gas)
I keep a pretty meticulous mileage log.
Highest mileage observed was 33.1 on a long trip and the lowest was 18.9 which was mostly city driving.

Most of my driving is highway at about 65 MPH.
I primarily use SUNOCO 93 Octane gasoline and at the beginning of each month I throw in a bottle of Chevron Techron to insure the injectors stay clean.
And of course I have the 6 Speed coupe.

 

Nice car to have for trips only!