Lately I have been adding a bottle of redex to every other tank of petrol when I fill up in the belief (hope?) that it will keep all the internal gubbins clean and hassle free.

I may be be disillusioned but research (admittedly on t'internet) indicates that the majority of folks are of the opinion that it won't cause any harm and may actually do some good.

Naturally the makers claim that it is the be all and end all of your worries vis-à-vis keeping your engine clean but I'm curious as to how many other owners use it.

Edited 27 July, 202527 Jul by Sofo

Waste of money, sadly.

Thanks for the response.

I'd be interested in why you think I'm wasting my pennies on it.

Most of the reviews I've read aren't definitive on any improvements in performance or MPG but on older engines surely a quick "clean" for the injectors etc. every now and then must be a good thing. 🤔

As my car is now 14 years old I can't see any harm in a little preventative maintenance and will probably bung in a bottle every 4th or 5th tankful.

9 minutes ago, Sofo said:

etc.

What do you think this might include? I don't think there is any such etc.

If you want to clean the injectors, it's almost certainly better to remove them and get them to someone who can not only clean but test the spray pattern afterwards. But petrol is a very good solvent for a lot of things, and you're already regularly passing that through them at some considerable pressure.

You'd probably be better making dure your engine is fully warmed (use oil temperature gauge rather than 'water' temperature gauge that's biased to show 90c) then give the car an "Italian tune-up", that is a good reasonable length journey ( 30+ miles) of higher revs. This of course is subject to the car not being such an old banger that it can't take more than dribbling along.

The occasional use of higher octane petrols with their greater cleaning additive packages. I try to go for two full tank loads together particular during "services" and MoT. (see attached below)

My wife says her 2015 Fabia Mk3 1.2 TSI seems to run better with use of higher octane petrols with their greater cleaning additive packages (I don't drive the car much but it seems that way to me too).

I used to drive 20-50 year old cars and I didn't always drive them slowly (but within speed limits).

MPG is difficult to calculate as if the car runs better you tend to push it slightly more even with out perhaps realising its so lowering mpg.

Good timely engine oil & filter, engine air filter and spark plug changes will help the engine run as good as it can - but of course the engine is a lot less important than brakes, steering, suspension, (all three include tyres), safety electrics (lights, blower, horn, etc.) reflective number plates (see and be seen).

petrol.pdf

Edited 28 July, 202528 Jul by nta16
ETA; newer version of pdf

Just use a decent fuel, almost all fuels have additives in them and they do an eyewatering amount of research into getting the dose right. If Shell have to do a million miles of test driving to "prove" that their fancy new additive fuel gives an extra 9 miles per tank full there's not much chance of your experience passing the bar of being proof, sadly.

Back in the day, when additives in fuels weren't so common, doing your own dosing could help, assuming you got the mix right.

The problem with trialling these things yourself is that its very, very difficult to rule out external factors that influence fuel efficiency and the influence on driving style when the driver is more conscious of fuel economy. Driving style can vary fuel consumption by upto 20%.

Having worked with the Petroleum industry, I can confirm that they would gladly sell their grandmothers for the chance of making very small additional market share in the huge market they operate in, so if Redex did deliver the improvements you hope for, they would have been bought out decades ago.

My Fabia loves a tank of Super unleaded and a motorway drive, and I can get almost 700miles range with that, but its still more expensive on a per mile basis than the same trip on regular unleaded.

Yeap you need to be selective as to when and where you buy the more expensive higher octane petrols with their greater cleaning additive packages. As you now the price per litre of any fuel can vary within different petrol stations a short distance from each other and vary more so a little further on.

I think my wife said it's usually about 12p per litre more for say Shell V-Power (other more expensive higher octane petrols with their greater cleaning additive packages are of course available, this is just one example at one point in time in one location) so if you're only worried about cost of mpg to that fill I doubt you'll get your money back just on that. Having said that there's very small Shell petrol station not far from us that just keeps the prices per tanker load and usually very good prices but sometimes they might even be a bit more expensive than other if there's been a sudden rash of fast frequent price dropping by other petrol stations around. My wife has filled up with Shell V-Power at less cost than a supermarket 95. She keeps an eye on petrol prices but they do change so much and often. The next town to us is she tells me 2p a litre cheaper for the same petrol and another smaller town just out of area less per litre still.

In my opinion if you have a 2011 VW then you really want to keep it as long as you can as it's probably better built and longer lasting than later models, I'd not want a 2017-on model for build quality and longevity plus all the annoying bottom-wiping computer dictating "features" and driver "assists" and "aids" and all the computer systems on the car that can and do go wrong or just play up in annoying ways. Computers plus over the air updates, wot could possibly go wrong. I've always found computer systems to be very trouble-free and robust over the last x-decades.

I would find add-in additives a right PITA with modern cars (90s onwards) I'm happy for the petrol companies to do the work.

3 hours ago, nta16 said:

...... In my opinion if you have a 2011 VW then you really want to keep it as long as you can as it's probably better built and longer lasting than later models, I'd not want a 2017-on model for build quality and longevity plus all the annoying bottom-wiping computer dictating "features" and driver "assists" and "aids" and all the computer systems on the car that can and do go wrong or just play up in annoying ways. .....

All those computer added doobries (as well as those ridiculous electronic handbrakes) are one of the reasons why I was discounting anything over a 20-plate when I was considering changing my car.

Very valid points on the alternative of splashing the cash on the odd tankful of "super" instead of Redex.

My thanks for all those views. 🙂 👍

As an aside I use an App on my Ipad (I don't mind computery doobries when they are not installed in a car) called simply PetrolPrices which constantly monitors the price of petrol (and Diesel) within a definable distance from your location. I find it very helpful.

They also have a website that does the same job (I am not affiliated in any way).

I don't think Redex will do any harm but running the car on the E5 fuel as opposed to the E10 will probably be the greater long term benefit. This will be particularly true if you do a very low annual milage. E10 fuel absorbs water and water is not good news in the fuel system of an engine.

Side Note It's why you should not run lawn movers and other garden petrol power tools on E10