Is The Mercedes Benz R129 SL A Future Classic?

Is The Mercedes Benz R129 SL A Future Classic?

In short - yes. In fact, the R129 is a current classic. It was a classic the day it was born in 1989.

Perhaps the more pertinent question is, will the R129 SL prove itself to be a good investment?

I’ve noticed that the SL is beginning to get more attention from investors, and not just your typical enthusiasts. Bruno Sacco's range of two door R129 SL roadsters are renowned for their fantastic build quality, timeless design and sophisticated craftsmanship; lazy owners have sent most shaggy examples to the scrapyard, meaning the market is rich with well maintained examples that have aged like the finest of wines. 

Future Outlook

The R129 SL is seen today as a highly desirable classic, but impressively practical and modern car. It commands an impressive average price in comparison to its successor, the R230 SL, not least due to its mechanical simplicity.

The value of the R129 has not declined for quite some time, in fact the trend is unequivocally upwards. Recent estimates suggest V12 models have surged in value by over 150 per cent in the last 5 years, with V8s not too far behind in excess of 75 per cent, and a conservative 30-35% increase in the value of mid-spec six cylinder examples.

With Generation X well and truly grown up, sporting grown-up sized pockets, the usual cycle is in full swing - ‘finally, I can get myself one of those SLs’ - that, coupled with the sweetest icing (it’s an SL dummy), means the R129 is becoming something of a no-brainer for investors.

History dictates that decent examples of this model will continue to appreciate, with the very best rising to many times their initial value. Facelifted models are generally more sought after, which come with a number of higher quality fixtures, fittings and parts.

            "The [R129] SL is handsome and has plenty of smooth power from its V6, V8 or even V12 engine. Best of all, it’s half the price of its SL R107 predecessor yet much easier to live with. Rare AMG models and special editions will increase in value more than standard cars" - Jeremy Clarkson 

R129 Model Investment Comparison Chart

Here is a summary of the good and bad habits of each R129 model, from the perspective of an investor.

R129 SL ModelThe GoodThe Bad
300 SL (M103)


  • Entry level price
  • Sturdy non-biodegradable wiring
  • A more classic feeling interior
  • Agricultural performance
  • Less modern trappings compared with later models
  • Limited diagnostics
  • Astronomical appreciation less likely
300 SL-24 (M104)


  • A purists dream
  • Ample power for top down cruising
  • A desirable slice of history
  • Sturdy non-biodegradable wiring
  • The KE-Jetronic fuel system is tricky to diagnose
  • Can be hard to find parts on the fuel injection side of things
  • Though rare, head gasket is prone to failure
SL 280 / SL 320 Straight-6 (M104)



  • Arguably MB’s finest 6 cylinder engine
  • Smooth, effortless power
  • Comparatively reliable with fastidious maintenance
  • Sensible choice for buyers less concerned with grunt
  • Engine wiring loom will need replacing depending on the year
  • Not quite as bombproof as it’s V configuration successor
  • MAS modules are prone to failure
  • Astronomical appreciation less likely outside of Special Edition offerings and low mileage unicorns
SL 280 / SL 320 V6 (M112)



  • Gutsy, bombproof engines
  • Easy to diagnose most faults
  • Parts aplenty
  • Interior build quality lacking
  • Mercedes no longer supplying coded key fobs, and corresponding ECU (update 2021: Mercedes are now supplying fobs)
  • The later central locking pumps are no longer available
500 SL (M119)


  • Pure grunt
  • A more classic feeling interior
  • A desirable slice of history
  • The KE-Jetronic fuel system is tricky to diagnose
  • Can be hard to find parts for KE-Jet cars
  • Throttle bodies are prone to failure, can be hard to source replacements
  • A generally tricky engine to tune
SL 500 (M119)


  • Superb M119 engine
  • Makes the best noise
  • Supremely reliable with fastidious maintenance
  • Post 96 cars are generally accepted as the best built V8 models - return on investment highly likely
  • It can bite you in the wet
  • Timing chain stretch possible with lackluster maintenance
  • Timing chains can jump on later types
  • Engine wiring loom will need replacing on earlier cars

SL 500 (M113)


  • One of Mercedes Benz’ most reliable V8 engines
  • Parts aplenty
  • Easy to diagnose faults - which are rare in the first place
  • Though an excellent all rounder engine, not a natural match for the R129 chassis
  • Missing the distinct tonality of the M119 V8 engine
  • The later central locking pumps are no longer available
600 SL / SL 600 (M120)


  • Flagship, top of the range
  • Oodles of torque
  • Guaranteed return on investment
  • Pre ’96 running issues are complex to diagnose
  • Expensive hydraulic suspension maintenance and repairs
  • Already beyond reach for many buyers

AMG Models

  • Rare and desirable
  • Guaranteed to hold if not gain value
  • Prohibitively expensive for many
  • Pre-merger cars are difficult to verify
  • Nigh on impossible to find certain parts

Closing Thoughts

The SL 500 (1997-1999) has by far the best build quality of the R129s. The Motronic engine is easy to diagnose and is near enough bomb proof. In my humble opinion, this is the best R129 to buy and a sure bet for investors.

Thanks, and good luck!


CEO, Founder

23rd Apr 2021 Carl

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