Looking for advice prior to buying a SLC - What MPG would I expect from the 280, 380 or 450 models?? - all advice welcome. - Either via the forum or my email - Thanks in advance
As you realise, MPG figures depend quite a lot on how you drive a car. Larger engines tend to have poorer MPG figures, but this is largely also because they provide better performance which tends to get exploited. Most modern engines are all broadly very similar in efficiency (fuel in to power out). However, if you have a large, heavy car, this will require more fuel to accelerate and more fuel to overcome the rolling resistance and air friction etc, than with a small, light car.
The difference in fuel economy under the same conditions will probably only show a few MPG difference between the engines listed. But in real life, if you have a V8, 450, I bet you will be tempted to use its power as often as possible with faster acceleration and harder braking, than if you had a V6 280. This makes the real difference in fuel consumption.
However, having experience of the smaller engine in a large car, I would recommend going for the 380 or 450. A lot of people woud say that the samller engine is adequate, especially around town. But around town is precisely where a larger engine works best as it gives you the necessary boost in pulling away from lights and in merging with the traffic flow at roundabouts etc. I think all the three are relatively tall geared and so all make good motorway cruisers, but I think a 280 can be more than a little underpowered in such a large, heavy car.
(Did you know that it only requires about 8kw (11 hp) to power the average car at a steady 40 mph? The rest of the power determines your top-speed and how fast you can accelerate.)
Here you are the consumptions for the 280, 380 and 500 SL/SLC (sorry, no data on the 450) as stated in a general world catalogue of 1981. Consumptions are in liters per 100 km. I'll let you do the conversion, since you are probably more familiar with english units than me (from Spain)
280 (2746 cc, 185 HP at 5800 rpm): between 9.3 and 17.7 liters/100km. No other indication stated, first figure is probably at a stable speed of 90 km/h and the second may be city cons.
380 (3818 cc, 218 HP at 5500 rpm): 11 to 18.8 l/100 km
500 (4973 cc, 240 HP at 4750 rpm): 11.1 to 20.6 l/100 km.
Regarding the 450, my father owned a 450 SEL in 1980 and I can tell you consumption was very high, and the ultimate reason to sell the car (cons was about 12-14 liters per 100 km at a stable speed of 90 km/h, and easily well over 20 in a sporty use). One has to take into account that the car mounted an automatic gearbox (I don't know if that's the case for all 450 SL/SLC´s) and was heavier than a 450 SL/SLC.
My advice would be to buy the car only if you are not planning to use if for frequent long journeys or as an everyday car. It will be a real pleasure to drive it for short trips.
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