just wondering wat the mpg on ur cars are mines is about 17

 

yeah. my 1990 300TE, which goes about 2 tons loaded, gets around that....it's killing us. Almost unaffordable to drive. We drive the BMW 325i which pulls around 25 mpg around town just because of that...I feel like an idiot for even firing either one of these suckers up to simply go get a gallon of milk...like I need 180 horse to go pick up some ice cream....just me though...cliff

 

My c220 does7.5 liters to 100 kms average which equates to 34-35 miles to imperial gallon.I recently did 2 trips of 180 miles each and because of traffic I had to keep under the speed limit, it did 41 miles to the imp gallon.I still complain about fuel costs though.

 

My 1999 E320 wagon with the M112 engine gets about 27 highway at 75 mph and averages about 23 mixed city and hway.If I set the cruise control at 60 she will get 29hway.



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1998 E320 w/167K on the clock gets average of 25-26 in mixed driving and always gets 30-31 on the highway. Premium Fuel in every tank and good synthetic oil changed regularly. No exceptions. My wife's Honda CRV gets 22 city and 24 hwy... it's lousy for such a small vehicle.

 

Just took a 5,200 mile trip with my son: '92 300 4Matic wagon. Averaged 25mpg.....but was chargin' around at about 80mph. Down around 70mph (and below) I got right at 27mpg. Not too bad for a car with 218,000 miles and a leaky head gasket. Had some 'tuner' crap cars ride my bumper at 80mph...at 135mph they disappeared in the rear mirror somewhere. Has some crazy Autobahn passing gear around 90mph.

Most fun I've had in a car for yrs, although I bought this car new, lost it in a divorce some two years later....now I have it back at last!

 

Miners an S320 M112.
I confirm Ohlords figures which I assume refer to US gall.

The onboard computer is surprisingly accurate (on my car) but may differ car to car. My figures are taken on a 500 mile round trip and confirmed brim to brim on a calibrated odometer. UK motorways have numbered mileage posts (16 per mile) and this enables odometer cal over a 200+ miles. A couple of car lengths in 200 miles is pretty accurate!

Fuel consumption is a function of vehicle size, aerodynamic performance (Cd), vehicle weight and driving style. Engine size/efficiency does impact figures but to a relatively small degree.

On the highway (constant speed) its all about how much energy is required to push the shape through the air. S Class has a Cd of 0.26 (one of the best figures in the industry) However its frontal area is greater than an E class despite its Airmatic suspension lowering the car at speed.

Around Town its all about vehicle weigh and driving style. The heavier the car the more energy is required to accelerate and driving style dictates how much energy you waste applying the brakes. Driving style can make a difference as great as 20%. Interestlingly it is best to get up to desired speed (and required gear) as quickly as possible. Its braking and scrub on cornering that are the enemy.

Large engined cars can actually return better fuel consumption under highway conditions than smaller engines vehicles dependent upon the small difference in specific fuel consumption at a given power setting, which in turn is linked to gear ratio and detail engine design. All engines have a "sweet spot" fort specific fuel consumption and this in turn dictates the best compromise speed to run at on the highway dependent upon vehicle gearing...and tyre size etc.

And just to make matters more confusing terrain and wind also impact consumption SIGNIFICANTLY. A 10 mph head / tail wind (not really noticeable from withion the car) is like altering your speed from 50 to 70 mph when you intend to conduct your test at 60mph.

Stuart

 

Stuart, It's long been known that bigger engines have a 'sweet spot' in fuel economy on the hwy because they're loafing-versus a little high performance four cylinder that working harder just to keep up. However, as was said, car weight/mass, aerodynamics, headwind, tail wind and side winds have a HUGE influence on cars, especially small cars that have to work at keeping consistent speed during high wind-given they have much less mass. Tires, overdrive, final drive ratio etc all factor in.

We have those speedo calibration as well on our Interstates, but they are far and few in between. Don't remember one on the whole big trip I just took. Personally, I'm only concerned with hwy mileage, as shooting around in a small town is 'disposable' gas to me. The way I look at it, if I can get 25-27mpg out of a vintage MB wagon on the hwy and have this much style, form and function, I'll let others praise their little econoboxes.

Case in point about 'sweet spots', I have a '89 Olds 4dr that gets 30mpg on the hwy most trips (V-6, FWD) and with its huge tank, I can go 500 miles on a tankful. I can't see any significant aerodynamics design with this car, but it does get the mileage.

Kevin

 

Hi Real1shepherd.

All engines have a "sweet spot" irrespective of capacity.
In the industry this is determined from the "fuel loops" which are the engines fuel consumption at differing speeds and loads.
The shape of these loops differ and it may be correct that on larger capacity engines the impact of external factors like headwind moves one away from the "sweet spot" more/less than on smaller engines.

I also love the "lazy" power delivery on big engines but the delivery of power at lower revs does not equate to better fuel consumption. However the typically greater torque produced by larger engines enables "longer" gearing to be used and this can lead to suprisingly good consumption on the highway (constant speed).
It is all about optimising the variables and not a big engine vs small engine argument.

Something i did not mention and which should be considered is that the greater the number of cylinders the greater the frictional losses within the engine.
Friction = reduced fuel efficiency!

30 MPG(US) which is 37.5 MPG(IMP) is indeed VERY good for an 89 vintage vehicle without the advantage of dynamic fuel injection metering (computer control vs carburretor) or maybe it was injected? However figures around 35 MPG(IMP) are entirely feasible.

Of course older cars didn't have todays mega wide tyres which gobble up lots of power in the form of rolling resistance.

The race is now on for improved fuel economy (worldwide) and I guess you guys in the States will increasingly come in line with the "European" way (small engines) which due to differentially higher fuel costs has been mindful of economy to a greater extent than prevalent in the States.
Taxation in the UK is now HEAVILY biased towards eco vehicles with VED (tax to permit a vehicle to be used on the road) dependent upon engine size/CO2 output.
Gas guzzlers" = anything above about 1.6 ltrs fall into a £300 per year category whereas anything larger than 2.0ltrs is about £400 from 2010.
Rough guide only.
IN ADDITION ALL NEW CARS ABOVE SIMILAR LIMITS WILL GET CHARGED A £!000 SHOWROOM TAX.

...and this new taxation framework is CURRENTLY retrospective back to 2001!,. As you may imagine there is some disquiet over this.

The WORLD is about to change!

Finally.
All UK "mile" posts on the motorways are numbered (16 to the mile) so it is possible to check accuracy over long distances without having to count every post. This is to enable your exact position to be determined should you require assistance. My regular journey is milepost 1 to 2560 = 160 mile.

 

Exactly so, and I was talking about 'loafing' with bigger engines on the hwy with cars of considerable mass. True that the econoboxes have their 'sweet spot' as well and that the greater mass, bigger engine cars suffer at low speeds and city driving with regard to mileage. Good point about friction-very hard for a heavy mass, V-8 (for example) vehicle to overcome frictional forces at slow speeds, while delivering good gas mileage. But then the econoboxes suffer in comfort, style and top end speed-gearing/tires being everything in hwy cruising. You can gear an econobox to have fantastic mileage with overdrive(s) and reduced weight, but your acceleration will suffer, high wind stability and so will your ride enjoyment factor. I've driven a number of Prius cars...they dart all over the road and are the most unsatisfactory driving experience for me to date. Just depends what the individual wants from an auto. I don't intend to give up everything I enjoy about driving just to brag about fuel economy.

My Olds is an enigma to me....it has fuel injection and a cam sensor that is read by the onboard computer. I think it's just a car that GM got right for a change. Big, heavy, ugly as hell, but an endearing engine set up. It has 245,000 miles and can still get 30mpg on the hwy-that's just a crazy premise for a heavy, American car. I almost hate to get rid of it, but against the MB, it's junk.

Don't misunderstand me....I want a decent carbon footprint, but as an American male, I also want some performance & style. There's no need to throw the baby out with the bath water-you can have both to a degree. However, that being said, I will not defend what I observed on my big trip through the western part of the US (seven states). What I observed in passenger cars and light trucks: at least 50% of the passenger cars on the hwys were larger, newer SUV's going on average 80mph. And over 60% of those were driven by aggressive males (sometimes females) with no more than one passenger (many were solo). And people wonder where gas consumption is going here(?)-yeah, right! To me, that's a crime on many levels and irresponsible 'alpha male' type mentality. Do people realize there's a big, ugly, new SUV called the “Armada”?? The name pun is so humorous that it must have been lifted from The Simpsons.

So now in the US we have 'crossover' vehicles that are unconscionably smaller, give better mileage and a halfhearted pitch to wean the 'alpha male' types out of their gas whoring, status vehicles. Like most concepts that really work, you have to start with education and children. Continuous 'zoom' commercials designed at the young male market defeat all that. In fact, auto advertising in the US is on a higher plane than even religion. What Ford, GM and Chrysler spend in one yr on TV advertising could feed the world for ten. The only thing they really get right, is how to extract disposable income from young males.

Kevin