Jaguar XJS or Mercedes SL (R107 and R129)? A comparison before you buy

In the 1970s, 80s and 90s the Jaguar XJS and the Mercedes SL belonged to the same segment: large, fast, luxurious two-door cars. Even so, they differ in body type, engines and production volume. In this comparison I set out the facts: dates, numbers, outputs and typical weak points. The details of the Jaguar itself are in the Jaguar XJS buying guide and in the article on the V12 engine.

Which Mercedes SL should you compare with the Jaguar XJS?

For the XJS's first 14 years its rival was the Mercedes SL R107, and from 1989 the R129. The dates and production volumes look like this:

The R107 was built in Sindelfingen, the R129 in Bremen. According to production tables about 68% of R107s went to the US, which matters for the European market: many cars in classified ads are imports from across the Atlantic, often in less powerful US specification. A large share of XJSs also went to the US — according to the Jaguar archive, 4,500 of the 10,361 cars built in 1988.

How do the body styles and character differ?

The basic difference: the XJS is primarily a closed GT coupé with rear seats (2+2), while the SL is a roadster. Each model, however, has versions that bring it closer to the other:

• Jaguar XJS — a coupé throughout production, the XJ-SC targa from 1983 to 1988 and a full convertible with a power-folding roof from 1988.
• Mercedes R107 — a roadster with a soft top and a removable hardtop. If you want a closed Mercedes from this era, there is the SLC (C107), built from 1971 to 1981, 62,888 cars in total.
• Mercedes R129 — a roadster with an electro-hydraulic fabric roof, a removable hardtop and an automatically deploying roll-over bar.

Photos from the MB Classics archive show the difference: the 1995 Jaguar XJS 6.0 V12 is a convertible with a fabric roof, and the 1994 Mercedes 500SL a roadster with the hardtop fitted.

How do the engines and performance compare?

Among the most powerful versions, the XJS V12 and the V8 SLs are close to each other; Mercedes only offered a V12 in the R129. The key versions:

Output data: the Jaguar archive and Ateupwithmotor (XJS), Daimler AG material (R107) and R129 model tables. The weights are similar: according to the Jaguar archive the V12 coupé weighed about 1,800 kg and the convertible about 1,900 kg; the R129 500 SL weighs 1,880–1,890 kg according to model tables.

The gearboxes differ too. The XJS V12 had a three-speed GM 400 automatic, and from 1993 a four-speed GM 4L80E; six-cylinder XJSs were sometimes manual. From the 1996 model year the V8 and V12 R129 got an electronically controlled five-speed automatic in place of the four-speed.

Which has the more modern technology?

The R129 is a generation younger than the XJS, and it shows in the safety equipment: the automatic roll-over bar and, from the 1996 model year, side airbags. The R107 and the XJS both date from the 1970s and in both the safety systems were added gradually — on the R107, ABS became an option in March 1980 and a driver's airbag in January 1982. The 1988 XJS convertible had Teves ABS as standard, and for the 1994 model year the XJS got a passenger airbag.

What are the typical weak points of the XJS and the SL?

In both models the biggest risk is rust, and in the versions with the largest engines, repair costs. Specialist guides point to:

Jaguar XJS

Rear wheel arches, sills, rear suspension radius arm mountings, subframes and floor; on the V12, the cooling system (coolant change every two years) and the hard-to-reach rear spark plugs. The full list of checkpoints is in the Jaguar XJS buying guide.

Mercedes SL R107

According to Hagerty UK, rust appears above the headlamps, on the bonnet, boot lid, doors, wheel arches, sills and floor, and around the windscreen and bulkhead; the bumpers rust from the back. Noisy V8 tappets can sometimes be cured with an oil change, and vague steering means a worn steering box. The central locking runs on vacuum and develops leaks over time.

Mercedes SL R129

The British specialist SLSHOP lists rust on the leading edge of the front wing by the bumper; on the M104 six-cylinder engines, head gaskets and the wiring loom; on early M119 V8s, distributor caps and the oil feed pipes to the tappets; on the five-speed automatic, failures of the electronic plate and oil seeping into the wiring loom. The roof control module under the rear seat can be damaged by jump-starting. SLSHOP describes repairs to the M120 V12 as very expensive.

What about parts and running costs?

Running costs are decided mainly by the condition of the car and the engine you choose. Jaguar Classic Parts officially supplies parts for the XJS, and its catalogue covers more than 22,000 part numbers. In both makes the twelve-cylinder versions are the most expensive to keep: in the XJS because of the complex cooling system and access to ancillaries, in the R129 600 SL — according to SLSHOP — because of the cost of M120 engine repairs. According to buying guides, the six-cylinder XJS 3.6 and 4.0 are cheaper to run, and Hagerty UK points to the 1985–1989 R107 300 SL as a sensible entry point thanks to its refinement and fuel economy.

Jaguar XJS or Mercedes SL — which one suits whom?

The choice follows from what kind of car you need, not from which model is "better":

• A closed long-distance car with four seats — the XJS coupé; the SL is a roadster, and the closed Mercedes of the R107 era is a separate model, the SLC.
• A roadster with a hardtop for year-round use — the Mercedes SL, in both generations.
• A V12 — the XJS in any year from 1975, or the R129 600 SL from 1992.
• Rarity — fewer XJSs were built than R107s alone.
• More modern technology and safety — the R129.

The MB Classics showroom currently includes a 1998 Mercedes-Benz SL500 — a facelifted R129, originally from the US market, with its roof mechanism recently serviced. In the archive of sold cars you will find the Jaguars 1987 XJ-SC, 1993 XJS 4.0 and 1995 XJS 6.0 V12. The Jaguar's history is covered in Jaguar XJS 1975–1996, and all the cars for sale are in the MB Classics showroom. More comparisons and guides are on the blog.