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Mercedes 420 SEL
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Discussion Starter · #1 · (Edited)
Doing a quick search, it looks like about 20-21mpg is an average depending on how you drive, with lead foot or egg.

Well, I was quite pleased to get exatly 22.5 mpg on my cross country trip. I was cruising around 80-85 mph for reference. (On another note, whether driving 65 or 85, it felt exactly the same in the Mercedes--so smooth).

Talking to the independent Mercedes shop I"m working with, thats pretty decent. So I'm wondering what its going to drop to when I get all my emissions stuff put back on the car? The mechanic owns a 420 SEL, too. (good sign), and he says he has only had about 19mpg.

I just think its ironic, put back on the emissions and get worse mpg-thus burning more fuel. Hopefully that won't be the case. Hopefully get my baby back this Friday. I've got a new console, zembrano shifter, and some brake pads to put on for a weekend project.

Hopefully this wind goes away, a tree fell on a house just across from me! It was a massive tree, fortunately everyone was ok.




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1973 450SL 2004 E320 4Matic Wagon 2019 Jeep Grand Cherokee
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16.9 to 17 city

I get 16.9 to 17 consistently in the city and get 21 to 22 on highway runs, usually around 75. Mine is fully muffled with all the pollution control crap. I was delightfully surprised when I brought the beast home on a 250 mile trip from its former home and hit over 20 in bad tune. Now, with the timing right thanks to a new timing chain, 21 is normal on a decent highway run.
 

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Depends on the day!
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13,337 Posts
Are you Really going to have to re-install the air pump??? I don't think the AP will drop your mileage that badly but you will have parasitic loses from clutch and belt drag. As well as added weight to lug around.

Jonathan
 

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Mercedes 420 SEL
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Discussion Starter · #4 ·
jhodg5ck said:
Are you Really going to have to re-install the air pump??? I don't think the AP will drop your mileage that badly but you will have parasitic loses from clutch and belt drag. As well as added weight to lug around.

Jonathan

Yeah, going to re-install the air pump. I realize its not a reliable part, nor necessary. However, I live in Gestapo Northern Virginia when it comes to emissions. I might know a shop or two that wouldn't look too closely and I'm pretty sure this car will pass emissions.

I also just want the car back to its original condition. There was a lot of fabrication done to make the car work, and if I'm going to take care of it in the future, would like to know where the hoses go and they are where they should be. I've worked with vacuum hoses before, and its a major pain to figure out what goes where--especially if you're not the one who did the moving of hoses and fittings.

Not fun on the wallet, but then again, my wife's friend just bought a $28,000 subaru--and its still a subaru.

Appreciate your help, though. And also sent you an e-mail for a CD manual.

:thumbsup:


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1985 380SE
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Don't most cars not even have those air-pumps? If you take it out (so it doesn't look like something is missing a belt) are they really going to be any the wiser?

There is nothing about that air pump to return it back to original, that's just our EPA crap.
 

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1990 Mecedes-Benz 420SEL
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1,217 Posts
Hey, GD, good luck on the weather; hope you are OK. I think the air pump will not contribute much to mileage losses - it really works ("pulls") only for a few seconds on startup (30?). Parasitic losses will be small. My 420 gets an average 21 on the highway, so you are doing great. That being said, I really do not care about my mileage... I love driving my car and there are always a bunch of SUVs within eyesight when I'm driving... Getting a lot lower mileage, like my GS470... 17 on a good day.

Dave
 

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1973 450SL 2004 E320 4Matic Wagon 2019 Jeep Grand Cherokee
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That's the way I look at it. They are to drive not to worry about. It's great compared to my Commander at a whopping 17 highway and 14 city. And if you really want to see awful, my 73 450SL gets a whopping 11 mpg of premium in the city and all the way up to 13 or so on highway. 20-21 of premium is an economy car. Interesting to do the math and figure out how little it amounts to on a 1,000 miles a month. It's less than most people spend at Starbucks.
 

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1989 500 SEC, Arctic White (147)/Sato Grey (7738) - Dark Blue Leather (262)
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Shortly after I got my SEC back in '99 I did a weekend trip from Newcastle, accross to Blackpool (if you know the roads you'll know that it's a mixture of fast Motorway, dual carriageway and two lane roads at varying speeds and my SEC averaged 24mpg over the whole trip which included some very brisk driving down the M6.

In urban driving it tends to get 18mpg.

However, I've had the engine rebuilt since then after the timing chain went through the rocker cover and haven't reallly tested it since. Will measure it over the next week or so and report back.

J.
 

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Smoke Silver '87 560SEC, Black Pearl '87 560SEL
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marlinspike said:
Don't most cars not even have those air-pumps? If you take it out (so it doesn't look like something is missing a belt) are they really going to be any the wiser?

There is nothing about that air pump to return it back to original, that's just our EPA crap.
Take a picture of the emissions label on the radiator bulkhead and photoshop the air pump requirement out of it. Print the label back out on photo quality paper and have it laminated with one sticky side so you can replace the stock sticker.

This is hypothetical of course.
 

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1983 Euro 500SEC AMG, 83 SEC custom convertible, 2x 84 500SEC, 02 w203coupe, euro 1985 300d
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'90 300 CE, '91 560 SEC, (R.I.P.) '82 300SD (sold)
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smack said:
That's the way I look at it. They are to drive not to worry about. It's great compared to my Commander at a whopping 17 highway and 14 city. And if you really want to see awful, my 73 450SL gets a whopping 11 mpg of premium in the city and all the way up to 13 or so on highway. 20-21 of premium is an economy car. Interesting to do the math and figure out how little it amounts to on a 1,000 miles a month. It's less than most people spend at Starbucks.
Thats interesting. I've owned three different Grand Cherokees, with the current one a 2WD instead of 4WD, and they all have averaged 14 city. Must be a Jeep thing...
 

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1990 420SEL, 1979 450SEL, 1973 450SE, 2003 C320S, 2005 C230WZ, 2005 E320W Avantgarde
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Gee, I must have a problem. I have a CA emissions 90 420SEL and get around 15.5MPG mostly highway. I have a new to me used engine with new chain, guides, seals, cap and rotor, plugs, wires, vacuum lines, etc.

I think it is my transmission. It withholds shifting even at light throttle until 3,500 to 4000 rpm cold, hot, ac on or ac off. It also kicks down at 3/4 throttle so I don't even hit the kickdown switch. On the highway it stays in 3rd until I reach 3,500 rpm, so it revs a lot more than it needs to which will be my slightly poor fuel economy. It also first gear starts at 3/4 throttle instead of kickdown or full throttle.

Otherwise it is a champ with 273,000mi and going. Both my 116s get 15mpg on the same driving mostly highway. I figure I can get 18 to 20 when I sort out the 126.

I don't know if the idle would effect the fuel economy much but the 126 idles in gear at the correct idle speed, but at almost 3 bar oil pressure. In neutral it pegs at 3 bar. That may be normal, but my worn out 116s both are idling at under 2bar and in neutral right at about 2bar.
 

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Sounds like you need to adjust the tranny cable tension....that should see you shifting earlier and not seeing kickdown so easily.

talbir
 

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86 560SEL
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The best mileage I have had with my 560 was 360 miles in one tank driving without air in the Fall from IN to IL and back. And with my S500c which I sold a few years ago was 498 miles in one tank. Just easy on the foot and steady speed.
 

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1990 420SEL, 1979 450SEL, 1973 450SE, 2003 C320S, 2005 C230WZ, 2005 E320W Avantgarde
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95 Posts
talbir said:
Sounds like you need to adjust the tranny cable tension....that should see you shifting earlier and not seeing kickdown so easily.

talbir
Thanks for the advice. That will solve my late shifting problem, and the fuel economy. It will also give me something to do at lunch time on my break.
 

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1989 560SEL
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I get 13 to the gallon with CA emissions.. We're soon to get the valves redone and at that get the timing chain done so... hope that does something.
 
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