Redex Fuel System Cleaner: A UK Driver's Verdict

In the vast and often perplexing world of automotive maintenance, few topics spark as much debate and curiosity as fuel additives. Among the myriad of products promising to revitalise your engine, improve fuel economy, and generally work wonders, Redex stands out as a household name in the UK. But does this ubiquitous 'petrol system cleaner' truly deliver on its ambitious claims, or is it just another bottle of snake oil?

For decades, motorists have been pouring Redex into their fuel tanks, hoping for a noticeable improvement in their vehicle's performance and longevity. The fundamental premise is simple: modern engines, despite advancements, can suffer from deposit build-up within the fuel system and combustion chambers. These deposits can hinder efficiency, reduce power, and even lead to costly repairs over time. Redex aims to combat these issues, but the real question for any savvy driver is whether it's a worthwhile investment.

Understanding Redex Petrol System Clean Up

Redex Petrol Advance Fuel System Clean Up is marketed as a comprehensive solution designed to tackle the five primary effects of engine deposits. These typically include issues with injectors, valves, and the combustion chamber itself. The product promises a 'pour and go' simplicity, recommending use every 3,000 miles. Its core function is to clean various components within the fuel system, ensuring optimal fuel delivery and combustion.

The concept behind such cleaners is that by dissolving and removing carbon deposits, fuel can atomise more effectively, leading to a more complete burn. This, in turn, can restore lost power, improve throttle response, and potentially enhance fuel economy. The appeal is clear: a relatively inexpensive preventative measure that could save you money on fuel and potentially avoid more significant repair bills down the line. But how do these claims stack up against real-world experience and expert opinions?

The Anecdotal Evidence: Does It Work?

Ask around the local garage or online forums, and you'll find a mixed bag of opinions on Redex. Some drivers swear by it, attributing smoother running, better acceleration, and even improved MOT emissions results to its regular use. Others remain deeply sceptical, viewing it as a 'magic potion' with unquantifiable benefits.

Online reviews often reflect this dichotomy. For instance, on major retail platforms like Amazon, Redex typically averages around 3.9 out of 5 stars, with a significant percentage (often over 50%) giving it a full five stars. This suggests that a substantial portion of users believe they experience positive results. Automotive blogs and review sites have also given it a thumbs up in product tests, citing improvements in vehicle performance after use.

One notable test, conducted by 5th Gear, reported a tangible increase in horsepower – a gain of 6 horsepower – simply from using a system cleaner. This kind of measurable improvement lends significant weight to the product's claims, especially for older vehicles where deposit build-up is likely to be more pronounced. The reasoning is sound: the older the car, the more accumulated deposits, and thus, potentially greater benefits from a thorough clean.

However, it's crucial to acknowledge the counter-arguments. Some experts, such as those at Auto Express, have expressed the view that fuel additives are largely a waste of money, suggesting that modern premium fuels already contain sufficient cleaning agents. This leads us to the heart of the debate: if these additives are so effective, why don't fuel companies simply incorporate them into all their standard fuels?

Redex in Diesel Engines: A Different Kettle of Fish?

A common question among diesel owners is whether Redex, primarily known for petrol applications, is suitable for their engines. The answer is yes, Redex does produce formulations specifically for diesel engines, but there's also anecdotal evidence of motorists using the petrol version (often referred to as 'red' Redex) in their diesel vehicles. According to Redex technical advice, if one were to use the petrol version in a diesel engine, it should be at double the concentration of the recommended petrol dose.

Diesel engines, particularly those with common rail injection systems, are highly sensitive to injector cleanliness. Clogged or dirty injectors can lead to poor fuel atomisation, reduced power, increased emissions, and even expensive failures. Many diesel owners report using Redex or similar diesel-specific additives, especially prior to their annual MOT test, to help ensure their vehicle passes the emissions component. Some users claim never to have had injectors serviced, even after accumulating over 150,000 miles, attributing this longevity partly to regular Redex use.

The discussion also touches upon the lubrication standards for diesel fuels. Some suggest that certain oil companies might skimp on lubricity additives, particularly in supermarket fuels, making a supplementary additive like Redex potentially beneficial. However, premium diesel fuels (like BP Ultimate or Shell V-Power Diesel) are specifically formulated with enhanced cleaning and lubricating properties, which proponents argue negate the need for aftermarket additives.

The 'Magic Potion' Debate: Premium Fuels vs. Additives

The scepticism surrounding fuel additives often stems from the logical query: if these products genuinely improve performance and efficiency, why aren't they simply integrated into standard pump fuels? Fuel companies do invest heavily in research and development to create advanced fuel formulations. Brands like Shell's V-Power or BP Ultimate are examples of premium fuels that boast enhanced cleaning agents and performance enhancers. These are often referred to as 'Optimax' or similar branded fuels, designed to keep engines cleaner and running more efficiently.

The argument is that if a standard fuel could achieve the same benefits at a lower cost by including a small amount of an additive, fuel companies would surely do so to gain a competitive edge. This leads some to believe that standalone additives are either redundant for modern engines running on good quality fuel or offer only marginal, unquantifiable benefits.

However, proponents of additives argue that while premium fuels are good, they might not be sufficient to deal with severe deposit build-up in older or high-mileage engines. An intensive 'clean-up' dose of Redex could provide a more concentrated treatment than what's present in even the best premium fuels, acting as a restorative rather than just a preventative measure.

The Old School: Decarbonising with Redex

For generations, mechanics and car enthusiasts have practised methods of decarbonising engines, and Redex has often featured prominently in these traditions. One classic technique involves dripping Redex directly into the carburettor of a running engine, often at high revs. This typically produces impressive clouds of white smoke from the exhaust, believed to be the carbon deposits being burned off and expelled. While visually dramatic, the quantifiable benefits of this method are often debated, though some claim it helped with sticking valves.

A more intensive method involves pouring a small amount (e.g., 25cc) of Redex directly into each cylinder of a hot engine, replacing the spark plugs loosely, briefly turning the engine over, and then leaving it overnight. The idea is that the Redex soaks into and loosens the carbon deposits on the piston crowns and cylinder head. Upon starting the next day, expect a prodigious amount of white smoke as the dissolved carbon is expelled. While this can purportedly clean the top end of the engine down to shiny metal, it's a more aggressive method and should be approached with caution, if at all, as it carries potential risks if not done correctly.

These older practices highlight Redex's long-standing reputation as a cleaning agent, even if modern engines and fuel systems have largely moved beyond carburettors. The core principle of deposit removal remains central to its function.

Does Redex Increase MPG? The Real-World Test

One of the most compelling reasons to use a fuel additive is the promise of improved fuel economy. It's notoriously difficult to quantify this without controlled testing, as many variables affect MPG. However, some user trials offer interesting insights.

A long-term test conducted on a nearly 19-year-old Peugeot 106 GTi, a high-revving 1.6-litre hot hatch with over 100,000 miles, yielded positive results. The test involved using Redex One Shot in every tankful, even switching from premium fuel to standard unleaded. The car's official factory rating for MPG was 33 MPG. After using Redex, the vehicle consistently achieved 34-35 MPG, sometimes reaching up to 387 miles per tank (calculated at 33 MPG, 360 miles was the lowest hit with some to spare).

This suggests that a 19-year-old car, well past its prime, was performing as efficiently, or even more so, than when it rolled off the production line. While the cost savings per tank might be negligible (around £2.50 for a One Shot bottle), the cumulative effect over time, coupled with potential benefits to engine longevity and performance, could make it a worthwhile investment for those who truly want to look after their vehicle.

The test also highlighted a minor annoyance: the difficulty in opening the Redex One Shot bottles, which often lack a convenient pull tab for the foil seal. This is a small point but can be frustrating when trying to quickly add the additive at the pump.

Comparative Overview: Redex vs. Alternatives

To provide a clearer picture, let's briefly compare Redex with other options available to the UK motorist:

Frequently Asked Questions (FAQs) About Redex

Q: Is Redex safe for all engines?
A: Redex is generally considered safe for use in most modern petrol and diesel engines when used according to the manufacturer's instructions. Always ensure you're using the correct Redex formulation for your fuel type (petrol or diesel).

Q: How often should I use Redex?
A: For their 'Advanced Fuel System Clean Up' products, Redex typically recommends use every 3,000 miles. For their 'One Shot' or 'Every Tank' products, they are designed for continuous use with each fill-up to maintain cleanliness.

Q: Can Redex damage my catalytic converter or DPF?
A: When used as directed, Redex is formulated to be safe for catalytic converters and diesel particulate filters (DPFs). Its purpose is to clean the fuel system and combustion chamber, not to introduce harmful substances into the exhaust system.

Q: Will Redex fix a serious engine problem?
A: Redex is a maintenance and preventative product, not a repair solution. While it can alleviate issues caused by carbon deposits (like rough idling or poor acceleration), it won't fix mechanical failures, worn components, or other underlying engine problems. If you suspect a serious issue, consult a qualified mechanic.

Q: Is Redex the same as OM15?
A: There's a long-standing rumour, particularly among those with an Air Force background, that Redex is similar to OM15, a mineral hydraulic oil with detergent properties. While both may have some cleaning characteristics, Redex is a proprietary fuel additive blend specifically formulated for automotive fuel systems, containing various detergents, dispersants, and other chemicals. It's unlikely to be identical to a hydraulic oil.

Q: Can I use petrol Redex in a diesel engine?
A: While some anecdotal evidence suggests it's been done (with a recommended double dose), it's always best practice to use the Redex product specifically formulated for diesel engines. Diesel formulations contain different additives tailored to the specific needs and challenges of diesel fuel systems and combustion.

Q: Does Redex really improve fuel economy?
A: As demonstrated by the Peugeot 106 GTi test, Redex can indeed improve fuel economy, particularly in older engines or those with significant deposit build-up. By cleaning the fuel system, it allows the engine to burn fuel more efficiently, restoring lost MPG. However, the savings per tank might be modest, making it more about maintaining optimal performance than drastic cost reduction.

The Final Word: Is Redex Worth Your Quid?

Ultimately, the decision to use Redex comes down to individual priorities and vehicle condition. For drivers of older, higher-mileage vehicles, or those experiencing minor performance issues like rough idling or reduced power, Redex could offer a noticeable improvement by cleaning out accumulated deposits. The anecdotal evidence, combined with some independent testing, suggests it can indeed restore lost horsepower and improve MPG, bringing an older engine closer to its original factory efficiency.

For newer vehicles or those consistently run on premium fuels, the benefits might be less pronounced, as these fuels often contain their own cleaning agents. However, even then, a periodic 'deep clean' could still contribute to long-term engine health.

Considering the relatively low cost of a bottle of Redex, especially when weighed against potential benefits like improved fuel economy, smoother running, and possibly avoiding more expensive repairs down the line, many motorists find it a worthwhile addition to their regular maintenance routine. It's a small investment that could help prolong the life of your engine and keep your pride and joy running at its best. While it may not be a 'magic potion' in the mythical sense, its ability to clean and maintain a vital part of your vehicle's operation is a tangible benefit that many British drivers continue to rely on.

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