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Redex fuel additive long-term trial

I'm undertaking a three-month trial of Redex fuel additives in my Mazda MX-5 to see if I can find any improvements in performance or economy (sponsored).

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Fuel additives have been around almost as long as cars themselves. Different products are available that claim to increase your horsepower, improve your fuel economy or generally make your engine more efficient.

Here in the UK, the market leader for fuel additives is Redex. The Redex brand dates back nearly 100 years, created in a time when the quality of petrol was generally poor and engines were far more problematic. Additives like Redex would help keep the fuel system clean of impurities and deposits that would build up inside your engine, helping your motor run smoother and last longer.

Of course, things have changed since then. The quality of petrol or diesel at your local service station has improved significantly, and you can buy premium fuels that contain cleaning additives straight from the pump. Engine design has moved on a long way as well, although newer engines are more sensitive to fuel quality. So is there still a need for fuel additives in the 21st century?

The famous Redex Round-Australia Trials

Back in my home country of Australia, Redex became famous in the 1950s for sponsoring a series of Round-Australia Trials. Standard production vehicles competed in a ‘race’ around Australia, covering up to 10,000 miles through some very inhospitable country – the main roads between state capitals were often still dirt tracks, let alone modern motorways. The fortnight-long events were front-page news around the country, with more than 150,000 spectators generally attending the start and finish in Sydney, and enormous crowds turning up at every checkpoint along the way.

Redex round-Australia trial FJ Holden
An FJ Holden participates in the Redex Round-Australia Trial (image (c) Holts)

The only modifications you could make to your car were to add a comfier seat (a standard vinyl bench seat was not conducive to 10,000 miles of racing around Australia) and additional fuel tanks. The latter were needed because petrol stations were sometimes more than 500 miles apart.

Competitors were also required to carry picks and shovels to help extricate themselves from inevitable trouble, as well as enough food and water to survive if they broke down. More than half the entries each year would fail to finish, as 1950s production cars were largely unable to cope with some of the toughest driving conditions in the world.

Rather than an outright race, the events took the form of a reliability trial. Bonnets and radiators were sealed up before the start, and competitors would earn points for completing each leg on time and without damage. Finishing late, damaging your car or having to conduct repairs would get you penalised. Breaking your bonnet seal to work on your engine would earn so many penalty points that you were basically out of the running. The winning crew was the one who dropped the fewest points over the journey, rather than the first across the line.

My Redex Round-Surrey Trial

I’m undertaking a three-month trial of Redex fuel additives in my 2013 Mazda MX-5 to see if I can find any noticeable improvements to performance or fuel economy. Now we have plenty of potholes and rubbish roads here in Surrey, England, but obviously nothing like outback Australia (and nor am I interested in finding any such tracks in my little Mazda!), but I’m still going to try and invoke the spirit of the old Redex Trials to make things a little bit competitive.

The whole idea is to see whether adding Redex to my fuel tank improves my car’s performance and/or economy, so we need to try and eliminate as many variables as possible. Clearly, this won’t be a properly scientific lab test, but we can take care of some basics:

  • I will be using regular 95-octane petrol, from the same petrol station each time unless that’s not possible for some reason.
  • I will be using a full tank of petrol for each reading, filling the tank to the first ‘click’ at the bowser and then running the tank down until the red light comes on.
  • I will check the tyre pressures at each fill, if possible, to make sure they stay at the correct levels
  • I have set the car’s display screen so that it doesn’t show either my fuel consumption or the trip distance, so I won’t know how I’m going until I fill up
  • I have access to two other vehicles, so if I’m going to be doing any trips that are unlike my regular driving and would yield noticeably different fuel economy (for example, a long motorway journey), I can use another car.

How it works

Redex 5-in-1 system cleaner and regular petrol cleaner

My normal driving pattern of mixed urban and A-road driving, with occasional motorway travel, generally yields a fuel economy average of about 30-32 mpg.

At every fill-up, I will be taking a note of my trip meter mileage and the amount of fuel added to work out my fuel consumption for that tankful.

I kicked off my Redex trial a couple of weeks ago, and the recommendation from the team at Redex was to add a 500mL bottle of their “Redex 5-in-1 Advanced Fuel System Clean Up”. This is a concentrated product that aims to clean deposit build-up from the engine’s fuel injectors. For subsequent fills, I will be adding a 90mL bottle of ‘regular’ Redex petrol system cleaner each time.

The products Redex have sent me are specific to petrol engines, but the company produces a similar range for diesel engines as well.

We will run the trial for three months, and see what we discover.

Redex 5-in-1 system cleaner in tank

This review is sponsored by Redex.

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Stuart Masson
Stuart Massonhttps://www.thecarexpert.co.uk/
Stuart is the Editorial Director of our suite of sites: The Car Expert, The Van Expert and The Truck Expert. Originally from Australia, Stuart has had a passion for cars and the automotive industry for over thirty years. He spent a decade in automotive retail, and now works tirelessly to help car buyers by providing independent and impartial advice.