gas mileage

[suzy]

i'm driving a 1970 manual 280sl.  i'm getting about 12 miles to the gallon (and that's considering i try and coast when i can!) which, with california gas prices what they are now, isn't anything to brag about.

is there anything i can do to better my gas mileage?  i use premium--more expensive but no knocking, and the car really requires it.

thanks

suzy adler

[Cees Klumper]

Basically the car's tuning needs to be gone over if you are getting that poor mileage. 16 or more MPG is considered normal average consumption, with some reporting higher figures than that. City vs highway driving makes all the difference, and so does the speed at which you drive when on the highway (i.e. 55 MPH is a lot more economical than 65).
If you cannot do the basic diagnostics yourself (cold start systems performance, CO readings when cold and warm, spark plugs, ignition timing etc etc) best to get a mechanic who is well-experienced with these sixties fuel injected Mercedes engines have a good look at it.

Cees ("Case") Klumper in Amsterdam
'69 white 280 SL automatic

[RBurg]

I drove from St. Paul, MN to mid Ohio last summer - mostly freeway and average 19+ with 75-80 MPH. Sounds like your car needs a good tune up with electronic spark system added. (I noticed a nice increase with electronic spark system)
Good luck with a nice turning.

Ron - Minnesota
71 280SL Tobacco "O GIGI"
97 E420 Silver Mist

[Raymond]

Suzy, it's a mystery to me.  My timing is dead on, the distributor was just rebuilt by Dr. Benz, the cold start valve, and FI pump were rebuilt by H & R, the plugs and wires are new, the valves, pistons, rings and bearings are new, the fuel filter is new and the lines and tank are clear.  I have checked the linkage three times, and I have played with the mixture and vacuum guage for weeks to get the idle smooth and the performance good.  The plugs are an even light brown.  I have just under 1,000 miles since rebuild and I just got 12.2 mpg on this last tank.

I was getting over 15 before the overhaul. I don't have a CO meter and the two shops I talked to won't use their meter on a car this old for fear of goofing up their meters. :?:  

If anyone has ideas, chime in. I'm out of airspeed and inspiration.

Ray
'68 280SL 4-spd Coupe

[mulrik]

I find that speed is a BIG factor. I got ~9km/l in Sweeden last summer going around with 70-90 km/h without too many stops. Then on the highway home 100 km/h it returned ~7. Remember that these cars have different diffs and automatic also decreases fuel economy. Another big thing is driving style. THese cars have enormous torque so if you are not off in a rush, shift gears upwards fast and use a higher gear than in your modern driver. And make it roll, they're also heavy cars.

And Raymond, find some people who are less fuzzy with their CO meter, it'll help you a lot.

A technical question. I've set my timing according to spec. Can you acieve anything (fuel economy) by doing timing by ear (that is up to knock at 3000 RPM and then a little retard off from there)
best
Ulrik


'67 250 SL Papyrus White 113043-10-000023

[JamesL]

I got 21mpg over the summer and have been told by my mechanic that's about right for the car. I use a combo of regular and premium, alternating fills

But that's imperial, not US gallons...which is 83% of the imperial, so that would convert to 17.5mpUSg

not much help but it's something to aim at!

[A Dalton]

<<I use a combo of regular and premium, alternating fills
>>

 A combo mix ?? ... or are you saying you use a tank of each , alternately ?? If the latter , I would certainly recommend you stay with the same octane always.  These cars do not have feedback controls for timng.

[DavidAPease]

Last summer I drove just under 6,000 miles in two weeks (San Franciso area to Blacklick, Ohio and back).  I drove as fast as I could get away with much of the time (75-80 MPH), through all kinds of terrain.  My individual tank averages varied wildly, due both to differing driving speeds and condidtions, and also to my apparent inability to fill the tank to a consistent level.  (I'd get a very low reading on one tank, and a very high one on the next, and they'd average out to something reasonable.)  My overall average was 18.3 MPG (U.S. Gallons), on an engine with about 5,000 miles on it since engine and FI pump rebuild.  I was quite pleased with this.

-David Pease
'66 French 230SL

[Cees Klumper]

David points out something I noticed as well - filling up the tank does not always fill it up, unless you hold the fuel nozzle in varying positions. Something to do with the shape/bend of the tube going down into the tank vs. the different-shape nozzles at different gas stations. In other words, if you don't fill it all the way up, you can indeed get wildly different readings. Taking an average over, say, 5 to 10 tanks, would be a good thing to do before you come to conclusions.
Ray - is it possible that the FI pump, although no doubt properly rebuilt, is set too rich? Rebuilt engine should improve things I would think.

Cees ("Case") Klumper in Amsterdam
'69 white 280 SL automatic

[mrfatboy]

18.5 mpg, fantastic.  I would kill for this.  I think I am about 13mpg. I know I am running rich.  I know that cylinders 2,3,5,6 are getting too much fuel from the IP.  I am just getting ready to do an IP overall with Hans. I'm just trying to justify $1000 for an extra 5mpg.

[JamesL]

Mr Dalton

I typically do a tank of premium followed by a tank of regular

I am not religious about this as sometimes I'll do 2 or 3 fills of regular to a tank of premium

Car runs absolutely fine on both - no discernable difference in performance (haven't checked consumption)

[mulrik]

According to the charts in the BBB from M-B a 250 SL is suppose to do 8,7 km/l with mixed driving (DIN), whatever "DIN" and "mixed" means.

In my opinion there's no need to put premium on these cars as long as you stick with the same octane. Petrol nowadays is much better refined and quality than when these cars were new.

Ulrik



'67 250 SL Papyrus White 113043-10-000023

[A Dalton]

quote:Originally posted by Tosh

Mr Dalton

I typically do a tank of premium followed by a tank of regular

I am not religious about this as sometimes I'll do 2 or 3 fills of regular to a tank of premium

Car runs absolutely fine on both - no discernable difference in performance (haven't checked consumption)

Very well.
 If your 113 runs as well on reg , I would assume it is timed for lower octane and the running of the higher octane has no effect. It is a rare 113 that will run well on reg due to the high compression of the head [9.3 on a 230/9.5 on the later].
 You may want to verify your compression specs...

[J. Huber]

One thing about the the Premium versus Regular debate is what octane are we talking about? In California, I have never found anything higher than 91. Regular is 87. So I would imagine the difference wouldn't be that dramatic. Yet, if Premium was a much higher octane than regular, maybe the difference is more noticeable??

In my case, when leaded went bye-bye here, my trusted Mechanic said Premium -- so that's all I've ever used since. As for mileage, it varies depending alot on stop and go driving versus highway. 16-18 is about my average. Not sure but I think I run a little rich.

James
63 230SL

[enochbell]

The discussion on octane requirements has gotten miles of lines of threads, but my read is that premium is important to protect from pre-detonation (pinging) on our old machines because they do not have sensors, as newer cars to, that adjust the timing to correct/prevent this from happening.  The danger of damaging pistons from the dreaded ping keeps me at the high octane pump, even if it does not give me noticeably better performance.

Best,

g

'64 230sl, fully sorted out...ooops, spoke too soon

[Ricardo]

When I bought an older 190e a few years back, I just used regular, even though it called for premium, after a few months it started running poorly. When I took it in to a european car shop to try out their service ( the MB dealer couldn't get me in for weeks) the german mechanic who owned the shop asked me, when I came to pick the car up, if I was using premium fuel. When I said "no" he gave me a little lecture about bosch injection systems being too finely machined to deal with "dirty" regular fuel. I switched and within a week or so, the car was running normally again...

[rwmastel]

quote:Originally posted by suzy

i'm driving a 1970 manual 280sl.  i'm getting about 12 miles to the gallon (and that's considering i try and coast when i can!) which, with california gas prices what they are now, isn't anything to brag about.

is there anything i can do to better my gas mileage?  i use premium--more expensive but no knocking, and the car really requires it.

Suzy,
I agree with Cees.  If you're not really familiar with the mechanical fuel injection, and don't feel like researching & learning, then let an experienced mechanic figure it out.  Tell us what part of California you're from and someone can suggest a mechanic.

quote:Originally posted by mrfatboy

18.5 mpg, fantastic.  I would kill for this.  I think I am about 13mpg. I know I am running rich.  I know that cylinders 2,3,5,6 are getting too much fuel from the IP.  I am just getting ready to do an IP overall with Hans. I'm just trying to justify $1000 for an extra 5mpg.

MrFatBoy,
5mpg x 16g = 80 miles added per tank.  To me, it would be worth it just to not stop for gas so often!  But the big problem with running so rich is that the extra unburnt fuel can wash down the cylinder walls, dillute the oil, and increase engine wear.  So, $1000 now for FI pump or $5000 later for engine rebuild (+ $1000 more for the FI pump that you previously ignored).

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[France]

Hi Guys (and finally another woman! now if I can just get her to add her red flag to the Frapper map!),

Remember also that octanes for Europe have always (I believe) been higher.  Premium is 98 and regular is 95, and I presume something at or north of 95 is what we should be using.  We had a laugh when we stopped in Basel the other day to gas up my 500SL and saw that Shell is marketing a 100-octane product...

Trice
1968 280SL US, signal red/bl leather, auto, kinder
Sarasota FL; Alsace France
There's two theories to arguin' with a woman.  Neither one works.

[Klaus]

There are two test methods to establish the octane number of a gasoline fuel, one resulting in the Research Octane Number R, or RON (German ROZ), the other in the Motor Octane Number M,or MON (German MOZ). By reason of the test setup, R is always higher than the M. In Germany, the posted octane number is always the R (ROZ), while in the US it is always (R+M)/2. That is why the identical fuel has a lower octane number in the US.

Klaus
1969 280 SL

[Benz Dr.]

Gee, I only get 10 km per liter.........or 22.5 MPG ( USG )



Dan Caron's
 SL Barn
benzbarn@ebtech.net
 slbarn.mbz.org
  1 877 661 6061

[rwmastel]

Dan,
Nice to see you back on the forums.  Get well soon.

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420

[JamesL]

Get well soon Doc

[J. Huber]

Hey Dan, thought you were just sick of us asking for free advice! Hope you are on the mend. Thanks for the health tips.

James
63 230SL

[CarlG]

I drove from Houston to Austin today, about 350 miles rt, at a fairly constant 70mph.  There are only a few small towns on the way so very little stopping.  Got right at 20 mpg for the whole trip.  It was a beautiful day for a spin, top down and listening to 60's music, aren't South Texas winters wonderful (when aided by global warming I guess).

1967 230sl (stick)

[n/a]

Hello, I was just reading your discussion(I don't get on as often as I should)& at least for the 230's the gas mileage was listed as 17.5 M.P.G. & typically thats what I get. My car runs best on regular. In the U.S. regular has a higher BTU than the other two. Don't ask me why but thats what the experts say.