560sl what MPG should it get? - PeachParts Mercedes-Benz Forum

robaincltnc · #1 09-14-2005, 08:06 PM

What kind of MPG can I expect with a 560sl? Lately I feel that the mileage has been super poor. I thought the problem was a dirty fuel filter (it was causing other problems) but now seem to watch the Fuel guage go down as I drive. As it is now it looks like I will get about 200miles to a tank. Its a pretty BIG tank. My "economy" guage seems to go to inefficient if I come off the line any more than almost and Idle. Is there something else going on?

gmani69 · #2 09-14-2005, 08:26 PM

I get anywhere from 10-14 mpg in the city and 18-20 on the highway.....maybe a little more than that if I can use the cruise control for a long period of time with a tail wind!
Greg

Roncallo · #3 09-14-2005, 08:40 PM

The 560 SL was rated at 17 Highway 14 City. I get about 16.5 highway usually driving at about 70 MPH. I only drive highway.

John Roncallo

cbdo · #4 09-14-2005, 08:44 PM

My driving is mixed but always at least some highway, and I'll usually see 18 or so; not as high as 20 but rarely less than 17 or so.
The "economy" gauge is actually a vacuum gauge, and therefore responds immediately to changes in engine loading or throttle position, but says nothing whatsoever about anything over time.

robaincltnc · #5 09-14-2005, 08:58 PM

Last I checked it looked as if I am getting around 11mpg. Mix around town and highway. Do you think something is screwy? Because my "economy" vacuum gauge is erratic..do you think that could be a problem..a vacuum leak?

Thanks for the help!

Strife · #6 09-14-2005, 11:23 PM

My car is well-tuned and running, tires up to standard pressure, brakes new and don't stick...even with a first gear start module, I'm getting 15 MPG/17 highway and I don't baby it. I think you have a vacuum leak somewhere.

t walgamuth · #7 10-16-2005, 08:47 AM

runs good and doesnt stumble on acceleration, you dont have a vac leak. that is a heavy car. if the plugs look the right color, light brown. you are running as designed. that mileage doesnt surprise me. an sl is about the same weight as my 500sec. the mileage should be about the same in town perhaps a little better on highway since the sl has less frontal area.

tom w

Jim H · #8 10-16-2005, 11:23 AM

Quote:

Originally Posted by robaincltnc

...My "economy" guage seems to go to inefficient if I come off the line any more than almost an Idle. Is there something else going on?

Yes, your manifold vacuum is decreasing. Don't worry, it is normal.

Your "Economy" gauge measures manifold vacuum, which is a simple indicator of engine power production. Gasoline engines have a high vacuum at Idle (throttled, throttle plate closed) and a low vacuum at Full Open (unthrottled, throttle plates open.)

When you accelerate, you need power, so you open the throttle and the vacuum goes lower.

At a steady cruise you should see higher vacuum, or more 'economy' than when accelerating, and when you lift your foot to slow down it should read really 'Efficient.'

So, according to your gauge, your best 'Economy' is idling or decelerating, but you won't go very fast...

robaincltnc · #9 10-16-2005, 02:14 PM

We plugged vacuum lines and I am now getting 13mpg..so what else do you think it might be?

Thanks!

MikeTangas · #10 10-16-2005, 03:52 PM

A bad O2 sensor can cause a major decrease in fuel mileage.

With the 560SEL I consistently post 15 mpg on an all city tank, 17.5 mpg on a mixed tank and 19-20 mpg all highway running 80mph.

87tdwagen · #11 10-17-2005, 04:44 PM

Quote:

Originally Posted by MikeTangas

A bad O2 sensor can cause a major decrease in fuel mileage.

With the 560SEL I consistently post 15 mpg on an all city tank, 17.5 mpg on a mixed tank and 19-20 mpg all highway running 80mph.

Emissions pieces are very tricky and fickle with fuel economy. If your ECM thinks you are in closed loop mode, it will richen the mixture and cause poor fuel economy. Does the exhaust blow black smoke, or smell gassy?

If your O2 sensors have not been replaced, change them, they have a service life of about 50K mi. and will throw off you ECM and fuel mixture real easily.

Good luck

robaincltnc · #12 10-17-2005, 04:51 PM

Yes,
The vehicle does frequently smell of gas. Best bet is the O2 Sensor. I don't know if its ever been changed..my O2 light does come on intermittantly.
Thanks,
rob

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