STP Ultra 5 in 1 Diesel Fuel System Cleaner 400ml , Restores Power and Protects your Engine, Enhances Fuel Economy, Mechanical Car Cleaning Products, Concentrated Cleaning Formula, Made in the UK

Great did it's job well, easy to use

Easy to use and a noticeable smoothness of acceleration and a perceived reduction in engine noise. Seemed to do the job and I was pleased. This was used in an Audi A6 with 80k on the clock. Used before a 4 hour main road drive. Filled up with diesel on the way back and noticed a change in noise and smoothness but still better than before product was used. Even thinking about buying some more.

Nice product

I turned my car on and noticed the dreaded engine light. After a faulty EGR valve was diagnosed and replaced I thought all was fixed. A week later the engine light appeared again. After it was looked into further, my 4 year old 30k miles Diesel Mini was found to be blocked with carbon and my exhaust pressure sensor pipe was completely blocked, which was also what clogged up the EGR valve too. I always try and use the premium fuel and take it on long runs at high revs to clear everything out but this had obviously not worked.I researched for a while to compare different additives that would stop this problem from coming back and I finally chose STP ultra diesel system cleaner. It states it is a 5 in 1 and it helps to save fuel, restore peak performance, cleans deposits, reduces wear and inhibits corrosion.I waited until I needed to fill up my fuel and, before filling, poured the whole bottle into the tank to allow it to mix easily when the diesel was filled up. I then took my car for a trip to allow the cleaner to start working in the car although it doesn’t say that you need to do that.I haven’t had any further problems yet and that was a year ago now but it took 4 years for the problems of the carbon build up to show. The box states that you should add a bottle to the tank every 4000 miles so I am going to follow this and time will tell to see if it does what it says it will. I am hopeful as there are many positive online reviews and videos for this product. I am not waiting until I have a problem again and would rather be proactive in trying to stop deposits damaging my car.Hopefully the carbon will either be slowed down or even stopped and I will update this review if I have any further carbon problems with the car.

This is pure magic. My 4 year old Renault Kadjar Diesel started showing all sorts of warning symbols suddenly. It became so extreme that I couldn't rely on the car for any long journeys. Even when I did the car kept me on the edge which worried me a lot.With cars, I am clueless on the mechanisms of a car even at a higher level. Having never heard of additives before, I took it to the Car dealer who charged me £99 as inspection charge.After the visit, the car was fine only for two months and one day when I was on the Motorway all warning symbols appeared and I had to make an emergency stop. The issue returned. This pushed me to a point that I had almost given up on it and started looking for Petrol cars.While searching the internet, I read hundreds of articles about fuel additives and decided to give STP a try. Went to the local mechanic, cleared all warning symbols, poured a bottle of STP Ultra 5 in 1.Took the car for a ride at 60mph for 20 minutes. Within that period, I started noticing the difference. The car was very smooth and gave me the exact driving experience I had when I bought it new. Now this is pure magic. Unbelievable.This product has saved me thousands of ££s that I would have lost, if I had gone for another car. One more thing I learned is that Supermarket fuel appear to be inferior. I was using them and that's when I got all these issues.

Just used this morning at 7am. It’s now 10:30 am. I drive my car on eco pro which shows me how many miles I’m saving. Now usually on my two morning journeys I save around 0.6-0.9 well since adding this and doing my normal two journeys I’ve saved a whopping 1.9 miles doing approximately 11 miles! Coincidence? I don’t think so! I will definitely be using it again and won’t be without it now.

No real difference

Use this in my 1.5 dci Renault Kadjar. It was running a little "rough" and lacking in power. Popped this into an empty tank at the pump, filled up, and after half a tank the pickup was much better, idling was smoother, mpg was back up in the 60s compared to low 50s. Very happy, will use this regularly.