If we've read our manuals, we know the manufacturer's don't like us adding anything other than a pre-selected range of oils, coolants and screenwashes. We are explicitly told not to use additives. However, look in your local motorfactors and you'll see all kinds of additives from those claiming to give extra bhp, to catalytic converter cleaners.

I tend to use redex injector cleaner from time to time, but don't add it religiously. I know fuel suppliers add cleaners anyway, but my understanding is that this stuff helps clean up deposits on the injectors. Although for all I know it could do nothing whatsoever as not being an experienced mechanic I can't strip the thing down to the injector jets to examine them.

I have also used Wynns Engine Stop Leak oil additive. There was no external leak at the time, although oil seemed to disappear, going from the top marker to off the bottom of the stick in about 500 miles. The additive seemed to stop this. However, later I got an external oil leak through my fuel pump blanking plate which I sealed with a liquid gasket, and now I have an oil leak which appears to be coming through the flywheel end oil seal (which I can't be bothered getting sorted due to likely cost). I have to wonder if this stuff potentially caused the oil leaks.

I guess the problem with additives is they tend to be something that few people know exactly what they're adding, and more marketing hype than anything. If I added anything and everything that said improves fuel efficiency I'm guessing I won't get the 100mpg that the manufacturer's would like you to think you'd get

Lets sort the snake oil from the decent stuff. Are there any additives worth using? What have you used to good effect? I mean a noticeable, or even better a measurable difference.

Also have any additives you know of caused any kind of damage?

For diesels - Millers Diesel Sport 4 - plenty of threads - defo not snake oil.

I was watching 5th gear or one of those programes and they tried 4 or 5 different BHP boosting products on the same engine in all the same conditions. They found that every single 1 lowered the BHP by 5! They were petrol products and iv never tried the Millers Diesel Sport 4 so cant comment on it. I like you just chuck some eredex in the tank from time to time!

I've been very wary about oil additives after a former colleague wrecked the engine of his 440 turbo after adding something or other (we're talking recon'd engine; not even rebuildable!)

I had also tarred fuel additives with the same brush in my mind, however the last time my car was in for service, they said they added injector cleaner, and whatever they did certainly helped reduce the plumes of black smoke that were coming out of my exhaust under heavy acceleration. This was even with the grotty filter that was still in at the time! A dose of that, and a new filter every 10k may be the way to go - especially now the Dragon box is in!

As for octane / cetane boosters (i.e. performance-enhancing additives, rather than 'maintenance' additives), I don't know why I'm wary of them - I just am! As anonymouse has said, certain types have a lot of support, and having looked at the label on a bottle of the stuff in Halfrauds the other day while waiting to be served, I can't imagine the claimed 'petroleum distillates' are any worse than anything that's in the fuel as it comes out of the pump. But still I'm wary! :ne_nau:

For diesels - Millers Diesel Sport 4 - plenty of threads - defo not snake oil.

I use this and it definitely works - the motor run smoother and mpg up by about 1-2mpg so pays for itself.

engine additives are a mine field,

Take Slick 50, it contains ptfe which if you read some owners manuals must never be put in the engine. Ptfe contents are pritty useless as more than 50% of bottle content gets trapped in the oil filter so in most cases pointless.

If any contain sulphur, teflon, chlorine all the main ingredients of 50 and nitrox ect then leave well alone as those ingredients are mostly pointless.

If the product is 100% petroleum (high end base oils) or full synthetic then they will work very well with a good quality engine oil.

Fuel treatments are usually very similar to the additives in the fuel station but some are more consetrated or special mixes to clean specific chemicals off valves,injectors ect

I sell the likes of STP, Wynns ect but mainly now sell and use Lucasoil product.

I have asked the garages that my work supplies and customers for feed back so my work can judge if it actually does what it says and always get positive remarks.

I would think unless you have a specific problem then additives in most cases is money down the drain.

Check out Lucasoil.com and then link to UK. They dont tend to say things that just make it sound good like some other oil companies so i tend to trust them more but thats my personel opinion.

For diesels - Millers Diesel Sport 4 - plenty of threads - defo not snake oil.

I bought some after everyone raving about how good it was. TBH, i only bought it because mine was getting a bit reeky...

Threw some in. Cleaned up the soot soooooo much. The back of my car after only a day back and forward to work (60 miles) used to be covered in soot. Now after a week, its still spotless. Cant comment on MPG, didnt feel any more powerful, but TBH, thats not why i bought it

Mmmm

I saw the 5th gear thing and we had the Millers guy in too

He said that on their bottle it does not state that it improoves performance , but I dont use it

I did however try the diesel additive to see what it was about

I have to agree it did help with the smoke that comes out the exhaust

Mine did a puff now and then , and it did seem to be better and the back of my car is ermmmmm dirty , so yes it does seem to have cleared the system out :lol:

Sarah

He said that on their bottle it does not state that it improoves performance , but I dont use it

On the bottle i have, it states "Better than new engine performance"...