450 SE Mileage?? - PeachParts Mercedes-Benz Forum

gbw · #1 11-16-2003, 07:48 PM

I am hoping to get this engine dialed in nicely. It has 105k original miles on it. After tuning and adjusting what would one expect for mileage on a 1973 4.5 liter in a 450 SE.

Tomguy · #2 11-16-2003, 10:10 PM

Psfred (Peter), a "Genius" here, says he gets 16MPG with the AC on (mostly highway driving, I would assume).
That's more than I could ever get. Of course, I have a lead foot, and I love opening up my throttle on more than rare occasions

I get about 13 or so. But I drive fast and heavy. With moderate driving, expect about 15MPG.

MikeTangas · #3 11-16-2003, 10:31 PM

I see 12-13 in town and 15.9 (best) on the highway. Heavy foot equals lower mileage, these cars are thirsty.

psfred · #4 11-16-2003, 11:43 PM

14.5 on the last tank, but I've been having ignition problems -- I see a Pertronix breakerless ignition in my future!

450SE will get worse, I'd expect 14 with gently driving.

I tend to drive Big Blue somewhat too fast, but I don't use the pedal much -- I've found that normal "tip-in" for gentle aceleration gives me between 60 and 65 on the country roads I normally drive. Except when I decide not to let some racer pass me, that is!

If you can resist the temptation to demostrate the hp this engine produces, 15 mpg is about what you can expect -- I remember a friend of mine saying that they got 14 from the 450 SEL in the late 70s, 12 from the 450SL.

Peter

wbain5280 · #5 11-16-2003, 11:43 PM

Maybe a modern fuel injection system would be in order. That K-Jetronic is rather neandrethal but I think a good OBD-II compliant system would work wonders for gas mileage, or at least one with an O2 sensor. Thoughts?

#6 11-16-2003, 11:56 PM

I would think that the cost of such a conversion would buy a lot of gasoline. IMHO, the smartest move would be to optimize what you have. Ensure that the fuel and ignition systems are in top shape, that the front-end alignment is in spec, tires properly inflated, etc. I think the w116 is a little more aero than the w108. Your highway fuel mileage may be slightly better than the w108 numbers previously posted.

wbain5280 · #7 11-17-2003, 01:11 AM

Good point. I'm a little spoiled on my current cars. I'll be getting an '89 300SE soon, W126.

#8 11-17-2003, 01:33 AM

The 300SE ties with the 560SEL as my favorite w126 model. Shame it was never imported with a 5-speed. Good luck with your new purchase.

Tomguy · #9 11-17-2003, 04:10 AM

Paul: also reminds me that a 560SEL was for sale off the Morgan Highway - looked pretty damn good, if I had the cash I would have inquired!

Remember this simple rule about gas mileage: Whatever you would do that would dramatically increase mileage, would cost more to do than to just buy that extra gas for many, many years! Make sure your tires aren't underinflated and that'll save you 2-3MPG.

#10 11-17-2003, 08:45 AM

Tom: You've piqued my curiousity re: the 560. What color?

Tomguy · #11 11-17-2003, 01:53 PM

It was black, and it was (is?) on the right hand side at that small station as soon as you get onto the highway from Keyser Ave. Saw it yesterday again!

psfred · #12 11-17-2003, 07:09 PM

A '73 450 is going to have D-Jet, not K-jet. Will be both more powerful and a bit thirstier.

It is possible to lean these things out a bit, so you can squeeze up to 16 mpg usually, if you don't have spark knock problems from running overlean.

Peter

gbw · #13 11-18-2003, 12:03 AM

Well Im getting ready to take my 1973 450 SE in now... Also has anyone heard of, or developed an opinion of the shops listed at the end of this saga?

Last night while driving home I heard a muffeled thump from what could only be my exhaust... I was in the fast lane coming off the gas (fast lane squatter ) and it lit up behind me. Man my heart stopped as I thought Id done the old girl in. This engine has just loved to keep on pulling but she is parked untill I find the problem...

Had it off the road for a year so I put some injector cleaner through it recently, two tanks worth. Started to smell a little fuel on start up during the cleaning. The rubber lines to the injectors leaked a little but that has stopped. Then came the back firing. I also noticed on the rare occasions that I try to start her in the cold she labors for few minuites, even after I used the injector cleaner. She seems to have more acceleration when warm now but the backfiring has me stumped...

This exact sequence of events happened a few years ago and they told me it was the fuel pressure regulator. "They" being the dealer here in Falmouth, ME. They had to ring a shop called German Auto Services in Saco Maine to jog their memories on early 117s... It was "fixed" and I drove around with 11 - 13 mpg average. I cruise 65 - 85 (occasionally I'll really let her go ) on the interstate and I keep it smooth around town, that nets me 11 - 13 mpg. I just changed the oil recently, didnt smell fuel in it. I'll check it again.

I disassembled this vehicle down to the unibody in 97. All new bushings etc on front end, new rotors bearings, shoes & calipers, shocks, some linkage ( dont ever let a hook tow you... ) Re plumbed the brake & fuel lines... didnt even consider cleaning the tank......dumb dumb dumb... German Auto checked engine for chain stretch, did tune up etc No injector work was necessary at that time. Had a proper 4 wheel align done. Painted her an Eighties MB Dark Green with gold pin stripping. The original light green was too hard to take. This 116 is a blast to drive. Hope she'll live...

#14 11-18-2003, 12:51 AM

I would strongly urge you to replace the rubber lines to the injectors. It's unlikely that they would leak, then spontaneously stop leaking. I have a bad feeling that things may get a bit warm underhood if you don't.

Tomguy · #15 11-18-2003, 01:16 AM

Mine backfired when it was set too rich, and the idle was set even richer.
Lean your MAP screw out 1/4 turn, and then when it's idling (warm, in park) raise your idle speed via the large slotted screw behind the distributor (2 hoses are visible going in and out of the unit). Clockwise leans it out (makes it idle faster). Having it overchoked will make it pop when you let off the gas.