Mazda RX-7: Land’s End to John O’Groats on sustainable fuel

By Charlie Calderwood

| 5 Nov 2024

Classic & Sports Car – Mazda RX-7: Land’s End to John O’Groats on sustainable fuel

It used to be that drivers only had to reconcile a car’s drinking habit with their bank balance.

We can rationalise it – no one is a saint and we all choose our environmental vices – but the growing trend for electrifying classic cars demonstrates that some can no longer bear the guilt.

Sustainable fuels, however, offer an opportunity to enjoy our cars, without modification, relatively scot-free.

So now is the time to subject this state-of-the-art liquid energy to a proper test, by taking a notoriously thirsty classic on the longest point-to-point road trip we can manage while remaining on the British mainland.

Attempting a guilt-free road trip in a thirsty Mazda RX-7 by driving the length of Britain on sustainable fuel

The Montego Blue paintwork of the 1992 Mazda RX-7 that’s going to transport us 1000 miles into the north looks almost black against the sea under Cornwall’s cliffs at Land’s End, and its compact, aerodynamic shape hardly brings to mind a gas-guzzler.

But this sports car is, famously, rotary-powered – and twin-turbocharged at that.

While the Mazda 13B engine’s nominal capacity is a mere 1.3 litres, the ridiculousness of that measure becomes obvious when you level it with the RX-7’s power figure: 237bhp.

And it’s thirstier even than that performance would suggest.

Cornish cliffs at daybreak

Autocar managed 15.5mpg overall in its 1992 road test, only just bettering the 14.7mpg a 422bhp Ferrari 512TR had logged a few months earlier.

To compensate for that prodigious thirst, Mazda fitted the RX-7 with a gigantic fuel tank for something of its size: 77 litres (17 gallons).

It bulges underneath the car and is why the boot floor sits so high.

Today that tank is full of completely fossil-free petrol from Sustain fuels.

The Mazda RX-7 at the start of its journey, about as far west as a car can get on the English mainland

Including the impact of manufacturing and transportation, the firm claims an 82% CO2 reduction by running its biofuel versus regular fossil-fuel petrol.

That saving won’t be insignificant, even in the next few days alone, because I’m going to be driving this Mazda RX-7 to John O’Groats.

Not only will I get to verify Sustain’s claims that the Mazda will run just as well on the green fuel as it would on regular pump petrol, but I’ll also be sampling the practicality of running a classic car on this newfangled offering.

If I’m honest, however, the part I’m most excited about is spending so much time behind the wheel of one of the Holy Grail Japanese sports cars.

The Mazda RX-7 on the Land’s End start/finish line

Before you even step inside the third-generation ‘FD’ RX-7, you’re falling under its spell. It’s in the all-time top five Japanese car designs for me.

The FD anticipated the trend for organic, rounded body shapes that would become commonplace by the end of the ’90s, but did so without looking bloated or formless.

Sensuous yet purposeful, it destroys the hackneyed criticism of derivative Japanese car design.

Compare the FD Mazda RX-7 with any contemporary Porsche or BMW and consider which was more original and modern in 1992.

The Mazda RX-7 had to do the first leg of the trip, from Land’s End to Bicester, on a single tank of Sustain fuel

Waking up at Land’s End at an ungodly hour of the morning reveals something thoroughly unmodern, though: deserted Cornish roads in the summer.

A tight schedule will force us on to fast motorways for much of this trip, but the opening stretch of A30 is a tight, twisty run between verdant hedgerows and a good opportunity to get to know this hallowed car.

The first impression of the 13B is that its power delivery is similar to any other highly strung turbocharged engine, except it is one that is exceptionally smooth.

The sequential turbos fill the gaps in the unit’s torque curve, and while it is still an engine that needs to be revved, it doesn’t feel gutless in its mid-range like the naturally aspirated units of past RX-7s.

The Mazda RX-7’s ergonomically excellent cabin

When the second turbo comes on song just south of 5000rpm, the Mazda surges forward and it’s the whoosh of forced induction that dominates the aural experience.

There’s none of the buzzing, almost motorcycle-like sounds that older cars’ exhausts emit – except for the electric buzzer that activates at a relatively tame 7000rpm to warn you off over-revving.

Unfortunately the road becomes a much straighter, less interesting affair once we get past St Ives.

The Mazda RX-7 has an unusual cruise-control system

There’s a button on the instrument binnacle labelled ‘cruise control’ that has no perceivable effect after a couple of tries.

Eventually I figure out that it activates the steering wheel controls – ‘set’, ‘cancel’ and one for ‘accel’.

It’s not for increasing the set speed, but instead works almost like the hand throttle on a pre-war car.

An overtake button perhaps? I’ve never seen anything like it.

Otherwise, the cabin is pretty conventional: simple, black plastic dash; rotary dials for the climate controls; and clear gauges that ape a Porsche’s in both colour scheme and for having the tachometer positioned centrally, in front of the driver.

The RX-7’s centre console is black plastic and pleasingly ’90s

The seats are brilliantly comfortable – supportive and hugging but not too tight – while the ergonomic layout of the gearshift, steering wheel and pedals is spot-on.

Behind, the rear seats found in some Mazda RX-7s have been deleted in place of a pair of storage bins that straddle the propshaft tunnel.

Well into the journey now, we swing east into Oxfordshire and our first fill-up at Sustain’s Bicester Heritage HQ.

This has the only pump that sells Sustain’s Classic Super 80 biofuel to the public, but the company plans to open four or five at other motoring hubs this year.

The Mazda RX-7 stops for a fill-up at Bicester Heritage

It’s similar to the petrol we’re using, except 20% of it is traditional fossil fuel, which significantly lowers the cost – to a still-dear £4.65 a litre.

For each car that covers the Federation of British Historic Vehicle Clubs’ estimated 1200-mile annual average, at 20mpg, that’s an increase in cost each year from £424 to £1264.

It’s a drop in the ocean compared with buying and running a collectible Bentley or Ferrari, but beyond the average MGB or VW Golf GTI driver for now.

The Mazda’s rotary engine makes 237bhp

Photographer Jack and I take a cross-country route towards the M1 from Bicester, but it’s soon clear Mazda’s RX-7 and Oxfordshire’s cratered roads aren’t compatible.

Though quite supple in its primary ride, the Mazda crashes over poor surfaces, with every disturbance sending a shock of rattles through the car’s stiff shell.

Mazda wanted a car that was as light as possible with near race-car-like rigidity, and it fitted the RX-7 with scant soundproofing, solid subframe mounts and, in European-spec cars, firmed-up suspension and a front strut-brace.

It makes for a brilliantly agile and responsive chassis, but it’s also seriously uncompromising.

‘The part I’m most excited about is spending so much time behind the wheel of one of the Holy Grail Japanese sports cars’

Before long we’re back on the motorway, topping up with more petrol on the outskirts of Sheffield before our first night’s rest.

From here on in our fuel is provided by a support van loaded with drums of Sustain’s finest and an old-fashioned hand pump.

Surprisingly, this manual process isn’t much slower than a forecourt fill-up, even with the RX-7’s huge tank, but a mat to catch any spills is essential.

The next fuel drop is at Windermere Boat Racing Club, where some of its vessels already run on sustainable fuels.

The Yorkshire Dales provide respite from monotonous motorways

It’s a chance to climb above the M6 and on to the A685, cutting through the Lune Valley.

It would be a brilliant driving road except that the RX-7 was clearly designed for Japan’s billiard-table-smooth tōge, not the surface of the Moon.

There is just enough flat Tarmac to enjoy the RX-7’s addictive turbocharged punch and cornering adhesion before the outrageously loud squeaking of the tailgate over bumps slows us down for fear of causing any damage.

The view back over the Mazda RX-7’s curvy bodywork

In fairness to the Mazda, it isn’t so thirsty that it needs a complete refuel to get from Sheffield to Lake Windermere.

From here we’re cautious because our next stop is north of Edinburgh, and I accidentally make the leg longer than it should be by directing us to the outskirts of the Scottish capital rather than Grangemouth.

This is where many of the components of the fuel in the Mazda’s tank are processed.

As I park the RX-7 for its fuel stop, I spot a few rotting potatoes that have fallen from a nearby conveyor belt among the stainless-steel silos.

The Mazda RX-7 joins sustainably fuelled racing boats at Lake Windermere

So what is in Sustain’s petrol? Well, it’s not synthetic.

That term encompasses everything from ersatz petroleum made in Germany from coal during WW2 to modern e-fuels, where huge amounts of renewable energy are used to electrolyse hydrogen from water and mash it together with carbon dioxide scraped from the atmosphere.

That can also be described as a sustainable fuel and is another promising technology, but it isn’t what we’re using today.

Instead, this is organically derived, but it isn’t bioethanol; it is a biofuel that is refined into gasoline.

Porsche-like dials in the Mazda RX-7

Unlike in synthetic compositions, the carbon is completely organic, coming from forestry waste, farm by-products and rejected vegetables.

As with bioethanol, all of the CO2 created from burning the fuel has been sucked out of the air by the plants that created the organic matter.

Unlike bioethanol, however, a car designed for traditional petrol needs no modification to run Sustain’s biofuel, nor will it see a drop in performance.

What comes out of the refinery is, in practical effect, identical to fossil-derived petrol of about 93RON.

Experiencing the Mazda RX-7’s sweet chassis balance

To bump that up to the UK-standard 95RON, 5% of this formula is traditional bioethanol – much the same as you’d find in the E5 at a petrol station.

That’s the last fill-up of the trip.

The Mazda has to cover the remaining 273 miles to John O’Groats in one hit, a similar distance to the first leg from Land’s End to Bicester, but on twistier roads.

Scotland’s infamous A9, the main road to the Highlands and one dripping in average-speed cameras, proves good for the Mazda RX-7’s economy, however: the fuel needle hits the three-quarter mark at the final overnight stop at Dunkeld, just north of Perth.

The Mazda RX-7’s signature pop-up lights

Up to Inverness, the A9 is as beautiful in its Cairngorms-edged scenery as it is frustrating.

After the Moray Firth, however, the nannying melts away, as does most of the traffic, and the road becomes part of the famous North Coast 500 loop.

Here, on smooth roads, the Mazda RX-7 is in its element at last.

It sits relaxed in its high gearing, but as soon as a slower car comes into view, you can drop a cog to overtake quickly and without fuss.

An accidental diversion towards Edinburgh gives a chance to admire another survivor of the UK’s corrosive weather

The section after Dornoch Firth, either side of Brora, is stunning.

Strips of quiet, largely straight, sweeping road are separated by tight corners climbing hills or circumventing lochs.

The Mazda’s tight throttle response, flat cornering and stable, weighty steering are a joy to embrace in this setting.

Wick has a bit of a ‘last town’ vibe, however, not least in its road surface, something with which the RX-7 driver will forever be obsessed.

Refuelling the Mazda RX-7 by fuel drum and hand pump, but Sustain’s network is growing

It isn’t that the car bottoms out or loses grip due to its firmness – its suspension keeps the tyres in contact with the Tarmac, and it can probably manage these rough roads more quickly than we are going.

It isn’t even that uncomfortable. But the constant rattling, vibration and shaking leave you scanning for a smooth path ahead or wincing when you hit a rough patch.

It’s got a slightly confusing character, the Mazda RX-7.

Fitted with leather seats, air-con and cruise control when such things were luxuries, it reads like a GT from the spec sheet, and that’s how, on a level road, its driving manners first register.

Driving this classic Mazda on the A9 north of Inverness is a highlight

It majors on high-speed stability, while its twin-turbo rotary engine delivers power in a serious, deliberate way.

It isn’t effervescent, chuckable fun like its MX-5 stablemate, yet its harshness would put off those looking for a GT.

Nobuhiro Yamamoto, the recently retired engineer who developed rear-drive Mazdas for decades, described it as a “pure sports car”, focused on being as fast as possible.

You’re not meant to smile behind the wheel of an RX-7; you should be sweating slightly, challenging yourself.

A Porsche 968 Club Sport is perhaps the Mazda’s most similar contemporary.

The Mazda RX-7’s factory strut brace

The poor roads from Wick to John O’Groats mean we reach our end point with some sense of relief.

Due to the hand pumps we’ve been using at our fuel stops, I can’t measure our economy exactly, but a rough estimate suggests about 21mpg.

The Mazda RX-7 has run faultlessly, too, as if it were burning any normal fuel.

Were it standard petrol, the car would have emitted 512kg of CO2 during the trip.

The Mazda RX-7 picked up some road grime on the two-and-a-half-day journey

That’s a similar carbon impact to a one-way economy ticket from Heathrow to Cyprus, or a new 60in TV.

Instead, we’ve contributed a net impact of 92kg.

As previously mentioned, this stuff isn’t cheap: the 100% fossil-free fuel we’ve used is not even on public sale, and Super 80 is nearly three times the cost of regular pump petrol.

Whether you look to sustainable fuel or an electric conversion, every solution to reducing the environmental impact of a classic car remains the preserve of the wealthy – for now.

But so, too, was fossil-derived gasoline in the past.

The Mazda RX-7 reaches John O’Groats after 999 miles and about 21mpg

If sustainable fuels can become that bit cheaper, which becomes more likely if those that are in the position to buy it do so, then we have not only a cleaner source of energy for our cars that doesn’t involve changing their character, but also a supply of fuel when the mainstream motorist is no longer buying the fossil stuff.

If that means I can return to the north-eastern Scottish coast in a Mazda RX-7 in the future, I’m on board.

Images: Jack Harrison

Thanks to: Mazda UK; Sustain Fuels

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