Buy & Tune Porsche 928 GTS

BUYING GUIDE We show you how to identify a good example of 928 GTS when looking for what many consider to the ultimate V8-powered Porsche.

The GTS was the only version of the 928 available to buy shortly after the last-of-the-line model was introduced to the world at the 1991 Frankfurt Motor Show. On the surface, the car wasn’t a huge departure from the GT that came before it (factory bosses described the GTS as “polishing the diamond”), but as is always the case with the evolution of Porsche products, significant changes had been applied to the car’s engine – now a 5.4-litre V8 chucking out close to 350bhp – and its already-capable chassis equipment, but that’s not to say exterior updates weren’t present.

Transaxle design legend, Harm Lagaay, introduced muscular rear wheel arches, wider alloys, a 911-esque rear reflector fill panel, a colour-coded ‘ironing board’ spoiler and other more subtle details intended to assist Porsche’s efforts in creating a recognisable family of cars through the use of trim design that could be applied to the 964, 968 and 959. While the changes didn’t deliver a supercar that offered unrivalled value for money, they did enhance the 928 in readiness for its last few years of life.

2,904 GTS-badged 928s were produced before production ended in 1995. Only 192 of them were right-hand drive, and typical of previous 928s, the vast majority were equipped with automatic transmissions. This was, after all, a car Porsche built for the job of cruising across the continent!

Today, the GTS is the most desirable 928 on the classic car market, with top-of-the-line performance and exclusivity commanding a premium price. Most owners have recognised the value in keeping their GTS in tip-top condition, meaning that those advertised for sale tend to be low mileage examples, but you’ll likely have to sit tight if you’re holding out for a specific colour and/ or one of forty-odd cars kitted-out with a manual gearbox. Whatever GTS you end up with, however, you’ll rest assured knowing you’re in possession of a practical, powerful, class-leading grand tourer representing the ‘last hurrah’ of a model that was intended to replace the 911. Here’s what you need to know when searching the classifieds.

The Cayenne SUV saw Porsche return to sales success with a front-engined, V8-powered model. The popularity of the Cayenne is largely due to its appealing sales price, unlike the 928 GTS which was one of the most expensive cars on the road in 1991.


The GTS was regarded as a special car from the moment it was launched, and most owners treated it accordingly. Of course, there are a few examples that have suffered neglect (where owners weren’t necessarily in a position to afford expensive corrective surgery when things went wrong), but on the whole, you should be able to spot a poorly kept GTS just by looking at it. They’re either really good, or really bad!

The 928’s monocoque shell is constructed from galvanised, zinc-coated steel, while its body panels are aluminium. This was an impressive exercise in fending off corrosion at a time when most car manufacturers were unfamiliar with the word ‘underseal’. Even so, more than twenty years have passed since the last GTS rolled off the production line, and unless the car you’re looking at has been sitting in a temperature-controlled storage facility, there’s every chance that factory-designed perforations in bodywork – the weakest points of the galvanising – will be showing their age. Make sure you have a good poke around.

It’s common for paint to bubble on the aluminium doors, wings and bonnet, especially if the car has been kept under a poor quality cover which traps moisture. This bubbling isn’t an indication of rust, and won’t result in holes in bodywork, but it is unsightly. A paint specialist will need to be called upon to fi x the problem. A paint thickness gauge will help you to determine if you’re looking at rear quarters full of filler. Don’t be afraid to spend time checking out every last part of the car until you’re satisfied that you’re paying a fair price. The seller shouldn’t rush you. If he does, then what is he trying to hide?

Get on your knees and have a look at the condition of the car’s sills. Early 928s feature exposed lower panels covered in protective stoneguard and paint, whereas the GTS features plastic side skirts that do a great job of hiding corrosion. Worse still, they can trap moisture if they’ve been removed and incorrectly refitted. On the plus side, they repel most road fallout.

The GTS inherited the S4’s big ol’ rear spoiler. On the later car, the spoiler is colour-coded to the host vehicle’s body. The part is positioned above the GTS’s model-specific badging and reflector fill panel. Make sure the latter is free of cracks.


GTS or no GTS, the most important part in correctly identifying a classic car is its VIN (Vehicle Identification Number). Open the car’s bonnet and look along its offside wing edge. You’ll see the VIN stamped clearly. Make sure it matches what’s printed on the car’s V5.

Elsewhere on the same document, you’ll see the car’s engine number. You can check this against the number stamped into the left front side of the 928’s V8. You’ll probably need a torch in order to see the marking clearly. Matching numbers is essential when it comes to retaining the value of an expensive classic, so be sure to ask plenty of questions if the engine fitted to the car isn’t the same unit listed on the V5, or if supporting paperwork (there should be plenty) highlights an engine swap. There may be a perfectly reasonable explanation (engine failure), but find out to be on the safe side.

Spend a couple of quid at where you can download a history report outlining any insurance claims, change of registration number, recorded mileage and whether there is any outstanding finance on the car. You should also enter the vehicle’s details into the DVLA’s online MOT database, a service which will return all passes, failures and advisories registered as far back as the car’s records are stored.

A build sticker highlighting factory specification and main dealer cost options is located under the boot carpet above the fuel tank. Check it out.


When buying a GTS, good service history is vital. Check to make sure there’s a complete stash of paperwork and no unexplained periods of being off the road. These cars hate not being used. Ensure all fluids, filters and timing equipment have been changed in accordance with the manufacturer’s instructions. Ask what grade and content of oil has been used. If you’re about to buy a car that’s been left standing for a while, invest in new timing equipment. This can be bought from Heritage Parts at a reasonable cost and is a DIY job, although you will need specialist tools.

If you don’t want to take on the work yourself, speak to a Porsche servicing and restoration specialist. It’s also a good idea to have the car’s fuel injectors ultrasonically cleaned.

They’re unlikely to have been serviced at any point in the past, but are prone to trapped dirt particles resulting in inconsistent fuel spray patterns that can inhibit performance. Expect to pay between £10 and £20 per injector. Contact the guys at Injectortune for assistance: Service intervals are recommended at 12k miles, with timing belt intervals every 48k miles. If your GTS is left standing for long periods (winter storage), then ensure you change the oil at least once a year.


By the time of the GTS’s arrival, strict emissions laws required the use of milder camshafts than had been used on the 928 S4 and GT. To compensate for an expected loss of power, engine displacement was increased to 5.4-litres through increased crankshaft stroke (up to 85.9mm from 78.9mm). A revised compression ratio, lightweight pistons, new connecting rods, updated Bosch engine management, improved airflow and electronic knock control contributed to almost 350bhp and 369lb/ft torque, with a surprising amount of power delivered down in the lower rev range.

In 1993, GTS engine block lower studs were replaced with bolts for improved strength and reliability, while a new design of piston ring strengthened skirts and reduced oil consumption.

Fortunately, the 928’s largely aluminium engine is over-engineered and under-stressed, meaning that most problems only occur through user error or neglect. Fluid leaks are rare, but check the condition of the oil and coolant anyway; a 928 run on an incorrect mixture of water/coolant will encourage head gasket failure. Check for white smoke from the rear, but don’t be alarmed to see this on start-up. It’s likely to be evaporating moisture in the exhaust system from where the car has been standing (full marks to you if you intend to use your new GTS as a daily drive!).

The Porsche V8 is an exceptionally smooth engine, with a linear delivery of power from the 3000rpm mark after an exciting release of torque and horsepower. A malfunctioning unit should be easy enough to detect. If this is the first time you’ve driven a 928, then it might be worth inviting someone familiar with the model to help evaluate the car that has caught your eye.

Don’t forget, fuel consumption isn’t one of the 928’s strong points. Put it this way, the 5.4-litre GTS will pass everything but a petrol station!

Total worldewide production of the 928 for all years was a smidge over 61,000 units, but due to the eye-watering list price of the 928 GTS, no more than seventy-seven examples of the 5.4-litre grand tourer are thought to have been imported to the USA!

Matching numbers is essential when it comes to retaining the value of an expensive classic



The 928 is a lazy grand tourer, ideal for long journeys and leisurely road trips. Automatic transmission was a standard feature, although manual gearboxes could be ordered as a cost option. A GTS with a manual gearbox is a rare thing. A right-hand drive manual is even rarer, especially in the UK where less than fifty were imported. The five-speed manual ‘box was a strong unit, with a differential-driven oil pump and a dedicated intercooler keeping toasty operating temperatures at bay. A heavy clutch on a manual GTS may indicate wear that will need to be addressed. Factor this into the asking price of the car you’re looking at. If you’re test driving a four-speed automatic, check to make sure that kickdown activates as the manufacturer intended. ‘Jerky’ shifting may simply be incorrect vacuum pressure, so don’t be tempted to think the car needs a new gearbox; the Mercedes-derived automatic isn’t known for being the most refined cog machine, although it rewards those who put up with its oft-staggered shifting by delivering a long service life.

The GTS comes complete with a Porsche Sperrdifferential (PSD) limited-slip differential similar in design to the unit found on the 959. The diff cuts in below 19mph when the rear wheels detect a loss of traction. A warning light shows up on the dash when the unit is doing its thing, so don’t confuse this with an error (although your driving style may be at fault!).


From the S4 onwards, 928 dash clocks featured a digital display providing important driver information, such as service interval alerts or error messages. In fact, the dash clock cluster is littered with more than twenty warning bulbs that should let you know if anything is amiss!

It may have become increasingly more refined as the years rolled by, but the 928’s interior design remained largely unchanged from the earliest cars of the late 1970s through to the GTS. The same Hasbro-esque control knobs sit each side of the steering wheel, while the dashboard splits at each end and continues its shape into the car’s door cards.

928 interior design is one of the model’s most celebrated features, so it’s no wonder Porsche left well alone. GTS seats tend to be full leather, with super-pale grey leather the most common variant. Aftermarket leather cleaning and conditioning kits can be bought from interior restoration and detailing specialists such as, Cambridge Concours (, and even the most damaged of leather can be brought back to life without the need for a retrim.

The GTS is a heavy car when compared to the earlier GT. The extra bulk is partly due to extra soundproofing, where Porsche wanted to achieve ‘the best of both worlds’ when it came to producing a fast sports car that doubled up as a comfortable cruiser.

Nevertheless, you may be looking at a car celebrating its twenty-fifth birthday, so expect the occasional rattle or creak from loose interior fixtures and fittings. Get your screwdriver at the ready!


The GTS came with ‘big black Brembos’ which are far bigger than the stoppers bolted to the S4, which were already a substantial improvement over the 928’s earlier anchors. New discs and pads in a variety of styles and compounds are readily available from the likes of EBC Brakes, Heritage Parts, FrazerPart and Design 911. ABS is a standard feature of the GTS. It stops as well as it shifts!

A thriving community of 928 owners exists in the form of the 928 Passion Group ( Founded by Ultimate Porsche columnist, Graham Martin, the group holds regular meets and provides advice and technical support to its many members.

928 interior design is one of the model’s most celebrated features, so it’s no wonder Porsche left well alone


GTS suspension is more or less the same as that of the S4, so you won’t have any trouble finding replacement parts. The 928’s legendary transaxle arrangement (engine at the front, gearbox at the rear) results in a near perfect 50/50 weight distribution, making the model one of the best handling supercars available in exchange for your hard-earned cash.

Independent suspension features in each corner. The car’s back end is bolstered by the 928’s famous ‘Weissach’ axle. Essentially, this a passive rear-wheel steering system that increases stability during turn-in by eliminating oversteer when you’re tempted to put the pedal to the metal when cornering. Fortunately, it’s a maintenance free system, so you should have nothing to worry about on this front. Hydraulic damping and well-engineered rubber bushes keep vibration to a minimum, but there’s always the risk of wear and tear on higher mileage vehicles, so keep an ear out for knocks over uneven road surfaces.


Before you’re tempted to tinker, make sure the car is properly serviced and is running without fault in a standard state of tune. You’ll be surprised at the positive impact fresh fluids, filters and other consumables will have on the driving behaviour of an older car. Importantly, consider whether you want to modify a GTS; standard examples are worth a lot of money, and modifications may impact the sale price you’re able to achieve when it comes to passing your pride and joy on to its next owner.

Porsche threw everything it had at revitalising the 928 as an exercise in breathing new life into a product line that had been around for close to twenty years. As a consequence of its enthusiasm for giving the 928 concept a reboot, the GTS has become the most sought-after model in the range. It’s an excellent car, but that doesn’t mean there isn’t room for improvement. ECU chips from 9Tuning ( are claimed to deliver an extra 15bhp and 18lb/ft torque without any additional hardware changes. Derestricted exhausts will improve throttle response and release more trapped ponies, while those keen on getting the best out of the GTS at the track might want to consider the benefits of increased displacement through the appointment of a 6.5-litre stroker kit designed specifically for the 32-valve V8.

Currently on offer at the 928 Motorsports website (, the kit will produce a six-litre engine if the standard diameter piston is retained, whereas upgrading to an enlarged sleeve bore and piston will yield a massive 6.57-litres. Machined from single billet 4340 steel and shot-peened for stress relief and surface hardness, the polished part is rated at a whopping 900bhp!

Those keen on getting the best out of the GTS at the track might want to consider the benefits of increased displacement


Body side strips and in-car cell phone installation were listed as cost options for buyers of the GTS at its original point of sale, as was a tow bar. Yes, you read that correctly. A tow bar. Few of these choices tempted buyers, although full leather and a CD player proved popular. Regardless of trim, any GTS is considered a good find today, with right-hand drive manual cars being the rarest. Here’s what we found when we scanned t’internet:


112k miles, right-hand drive, automatic, three owners from new, new engine mounts, new ignition system, re-trimmed grey leather, walnut veneer, respray, refurbished wheels, comes with full MOT £42,000


102k miles, right-hand drive, automatic, black leather, walnut veneer, new tyres, refurbished ECUs, new radiator fan, aftermarket head unit £34,995


29k miles, right-hand drive, manual transmission, linen leather with blue piping, aftermarket head unit, new timing belt kit, mechanical overhaul, owned by director of Hexagon Classics £69,995


Heritage Parts

Design 911

928 Motorsports

EBC Brakes

Porsche Classic Partner


Cambridge Concours



Mr 928

JDS 928 ECUs

928org mailing list


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Jean-Claude Landry
Jean-Claude is the Senior Editor at, and, and webmaster of He has been a certified auto mechanic for the last 15 years, working for various car dealers and specialized repair shops. He turned towards blogging about cars and EVs in the hope of helping and inspiring the next generation of automotive technicians. He also loves cats, Johnny Cash and Subarus.