SEL) were exclusive to W109 with odd exception of standard wheelbase 300 SEb (1965–1967), which was designated as W108. The smaller six-cylinder inline engines (250 S/SE and 280 S/SE/SEL) were assigned to W108 only. Both eventually received the V8 engines in 1967 (W109) and 1970 (W108). W109 was more luxuriously appointed than W108, featuring burled walnut dashboards, automatic transmission, and power windows along with optional air conditioning system. Most obvious distinction from the W108 were door window frames and a-pillars fully finished with polished metal bright trim. The W108 and W109 had different types of suspension systems: W108 retained the steel coil springs and oil-filled shock absorbers while W109 used the self-levelling air suspension. First Series, 1965–1967 The W108/W109 premiered at the Frankfurt Auto Show in 1965. The initial model range consisted of three W108s (250 S, 250 SE, and 300 SEb) and a sole W109 (300 SEL). The inline-six engines were carried over from the previous generation with mechanical refinements. The 2.2-litre M180 engine was enlarged to 2.5 litres while the fuel-injected 3-litre M189 version was carried over from "300 Adenauer". The 250 S was fitted with 2,496 cc M108 engine with dual two-barrel downdraft carburettors producing at 5,400 rpm. It could accelerate to in 13 seconds for manual and 14 for automatic. The top speed was for manual and for automatic. The 250 SE had the same engine as 250 S except for fuel injection system and different engine designation (M129). With increased engine output of at 5,500 rpm, 250 SE was one second faster to 100 km/h than 250 S and had higher top speed of for both manual and automatic versions. Both 300 SEb and 300 SEL were fitted with 2,966 cc M189 engine. The engine was an updated version of M186, originally developed in 1951 for Type 300 "Adenauer", with Bosch mechanical fuel-injection system that calibrated the optimal fuel mixture automatically based on throttle pedal position and movement, engine speed, atmospheric pressure, water temperature, and driving conditions. The engine's output was at 5,400 rpm, and 300 SEb and 300 SEL could accelerate to in 12 seconds and reach the top speed of ( with automatic transmission). The production figures for the first series from 1965 to 1967 showed 129,858 of 250 S/250 SE and 5,106 of 300 SEb/300 SEL. The tiny production figure of 300 SEb/300 SEL reflected the higher sales price with luxurious appointments,