The Cars

Both the proudest members of the 6 series fleet, the 635Csi and the M635Csi (M6) turned some heads in their day. The smooth, suave and stylish 635Csi complements the Coupe category with BMW's luxury interpretation of a performance two-seater, while the M6's devilish speed and acceleration threaten to unseat all reason in the driver and incite blissful euphoria. Nevertheless, both are classic Grand Tourers matched only, possibly, by the Mercedes W116 450SL, which, by the time the smooth sixes arrived was looking a little tame. Both cars are excellent operators, described as threateningly 'shark nosed' by some, conversely, when stationary appear more disciplined and inviting. The elegant side-on profile really matches the image of the 6 as a car of 'Monte Carlo-ish' long and reserved charms. Coupled in the with the discreet 'M' badge on the M6, smaller mirrors and a slight spoiler on the rear and you have yourself a pair of vehicles whose attributes stop thankfully short of any ostentatious assumptions and bring out a silent but highly visible magnificence.

The 635CSi

The 635Csi is an excellent example of the 6, this particular luxury model (pictured below) is the Highline edition of 1989 cranked out to increase sales in the last year of 6 series production by BMW. It was designated the 'L6' in the US, suffering from lower power output courtesy strict US pollution emission legislation and was only available with automatic transmission. This one, coloured Misano red, sports larger bumpers, leather which extends up the sides of the doors, dashboard and headlining. Coined by an owner for having three points of superb strength, he articulated power, comfort and suspension.

(Left) The sleek, black leather interior of the 635CSi, leather also comprised portions of the dashboard and side doors. This 1989 example is in relatively good condition and exemplifies the luxurious image of the 6 as an exclusive Coupe. Automatic shown. Click image to view magnified version.

(Right) The mechanical entrails of the 635CSi, an M30 3.4 litre engine sits at its heart, also that which powered most of the E23 7 series. Click image to view magnified version.

The M635CSi (M6)

Pictured (below) is the 1989 M6 Macao blue 6 series, a recipient of 60bhp more grunt than the 635Csi, it offers performance as its cornerstone. Described by many as a fabulous all-round car, whose build quality, comfort and ride are outstanding, it is not a model without imperfections. None crippling of course, but possibly BMW didn't fully anticipate the 'character' the M6 would exhibit after being doled out so much power, "M6 power demands respect and you have to watch the rear end, even in the dry." (Mick Charman, BMW Car) Such stability problems aren't major blemishes on the appeal of the M6, however, whose driver's seat is aspired to, precisely on the basis of power.

(Right) The heart of the M6, the S38 'M-power' in-line 6 cylinder with 3453cc of capacity. It's engine was more or less directly derived from BMW's successful M1 racer. Click image to view magnified version.

(Left) The white interior of the M635CSi, this specimen has seen some better days, but the immutable BMW aura remains evident in this high-performers' cabin. Manual shown. Click image to view magnified version.

Performance

While both engines claim roughly the same capacity (M6, 635CSi, 3453cc and 3430cc, respectively), it's the M6 which really shines through on the 0-100km/h or 0-60mph benchmark. And its no wonder, BMW built the big 'M' to be the faster car, with twin cam and 24 valves to the slower 635CSi's single cam and 12 valves.

It's nothing less than a convincing defeat for 635CSi, which submitted to the inherited M1 power of the M6. The M6 blasted forward to 100km/h from zero in a tidy 6.0 seconds , while the arguably more luxurious and stylish, albeit more sluggish 635CSi reached the same achievement in 8.4 seconds .

We find some reason for the 635CSi's prior defeat here where the M6 measured 210.21kW and the 635CSi just bumped over the 160 mark at 161.7kW .

The M6 won the efficiency round, boosting 1 mile more covered for the gallon than its counrerpart. The fuel consumption test was based on "composite" figures, which measure fuel usage over a mixture of highway and urban driving to derive an aggregate result. The M6 scored 19mpg , while the 635CSi , 18mpg .

Specifications Wrap

The Verdict
Performance probably doesn't represent the most fair comparision between both these fine motor cars. They are equally different and suited to two different types of driver. The M6 is a faced paced beast whose spirit wants to leap out upon the road to race the wind, while the 635CSi is more relaxed in it's design seeking that smooth, luxurious drive, opening up well on those rural roads and crusing wonderfully even at higher speeds. Nevertheless, the M6 dominates both the power and acceleration categories, not surprising considering its masterpiece of an engine (from the M1), perfectly tuned and suited to its racing ambitions. The M635CSi (M6) retains the fuel prize, while not a landslide achievement, it's greater power is matched with savings at the bowser. Where the 635CSi does lead the pack is in its luxury charms, its black leather interior (in the Highline and L6 models) clearly blitzes the M6's humble offering. It claims a sleekness and durability that shines up upon most modern cars even today (2003) while the M635CSi (M6) is looking like a sadly dated excuse for style. If you own one, your lucky and if your looking to buy, it's well worth it. The M6's is really fun to drive, while the 635CSi is better suited to a soak-it-up relaxing spin in the country, letting the automatic do it all.

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