njgilligan

I had a 430, and saw as good as 24.5mpg on long trips. Now I'm thinking of getting a 55 AMG. I've heard stories about people getting up to 29mpg in a 55; even with the slightly lower differential ratio (2.87 vs 2.82), I find this hard to believe.

I'm not concerned with city driving, I know I'll be tearing through fuel in stop and go, but what's the best mileage you've gotten out of your 430 or 55 for a long highway stretch?

slowsky

24 hwy (85mph)/ 15 city

GiZzO

Im always in light to heavy traffic, whadda ya expect im in LA. Best i've seen is 22MPG trip to San Deigo.
I avg 17.5MPG per tank, mostly city driving. I romp on it daily. Nice high speed bends to and away from work.

MarcusF

I've heard of 29 MPG, but it was in a 430, not a 55. A 55 accelerates faster, has a higher top speed, brakes in shorter distances, and handles better, but it does not get better fuel economy than a 430.



That said, I've never met anyone with a 55 who minds the difference in fuel economy. I know PLENTY of 430 owners who mind the difference in performance.

LawRens

yeah. having an m113 e43 engine always leaves more power to be desired. good power mind you, but still never enough. the best ive netted was 22.5mpg in a tank, and that was driving 50-60mph on freeways... i dont know how you guys do it.

njgilligan

I agree about the 4.3 motor (which is why I'm thinking 55 this time). Fuel economy is not really a deciding factor, I just wanted to get an idea of what to expect.

Marcusf, thanks for the pic, although I'm still a bit skeptical. There has to be a 300 mile downhill section that ends in 104º weather somewhere in the world.

Thanks all, keep em coming.

Chappy

Quality tires can also improve your mileage. I can't recall the exact mileage figure, but I've had a best of 27+ on long highway trips (75-80mph average)

92bubble

damn...i wish i could get 29mpg....i only see 25

njgilligan

Hey Chappy, wow 27+ is impressive. What kind of tires and what size were you running?

MarcusF

Someone else thought that was a downhill or doctored photo. A good tune, good tires, and cruise control are all I use. 300 miles, all downhill, driving in 104 degree weather without the AC, and I just happened to pick that route and record the mileage is highly doubtful. Here's another one. Look at the mileage. A one thousand mile hill would cover more than a third of the United States (Los Angeles to Miami is 2700 miles). Also, 17+ hours covered numerous cold starts. Of course, it could be that M113s really are reasonably economical.

njgilligan

I didn't realize that was your car, that's awesome. Are you talking a custom tune or one of the chips you can order online? What kind of tires?

Chappy

Factory 17 monoblock IIs and Michelin PS2s in factory sizes. Since I rarely drive my 55 more than a couple hours at a time now, it's difficult to determine what my "best" would be today.

I'm now running larger wheels and tires. When I drive now, it is for pleasure only and fuel mileage is not even on the agenda.

MarcusF

When I say a “good tune”, I mean spark plugs, air filters, fuel filter, etc. are all in spec. Basically, all the maintenance that’s supposed to be done, is done. A decent alignment too. I don’t have a custom tune or chip or exhaust - my car is stock. Naturally that mileage doesn’t reflect bumper-to-bumper slogs through Southern California, but you’ve seen the results when I average over 50 MPH. Nothing special about the tires other than they are kept properly inflated and I run name brand rubber. Not that anything is wrong with running a brand-x tire, I just happen to prefer name brands with a double A rating (traction/temp) that don’t howl or tramline (I read the Tirerack reviews). I’m currently running Continentals. If you get a 55, and it runs right, open road fuel economy will be pretty good.

njgilligan

Ah, makes sense. I take these items (plugs, filters, oil etc.) to be a given, especially for someone with such a nice car, but I guess not everyone thinks that way. I doubt there's much, if anything, in the way of fuel economy to be gained by modifying the ecu on a Merc anyway.

That tire inflation guide is really helpful, or at least interesting. I don't think I'll be doing that procedure too often, but I'll definitely give it a shot to see where I'm at.