STP Diesel Fuel Additive Treatment Bundle, Includes Diesel Injector Cleaner and Ultra 5-in-1 Diesel System Cleaner, Cleans Injectors and Restores Performance For A Smoother Engine, Made in the UK

It does the job, the engine seems less vibrate during cold start and more responsive for my 10 years old C4 Picasso.

This stuff does exactly what it says.. I get a good clear out of particles after adding and more miles to a full tank.. I have a 2011 car and this is my new go to.. I use once every 2 to 3 months as I clock up some miles and works better than previous ones.. definitely on re order

Good priced bundle. Arrived on time - although courier left package on front door step instead of back door as instructed. Not yet used as waiting to reduce fuel in tank before treating. Hoping for improvement in MPG and performance...

An excellent summer drink for all diesel cars with any mileage.

Great value just right

cured my diesel knock/stuck injector in one tank of fuel.

Exactly as described. Good product have regularly used for my vehicles, though this deal seems to be a good price

I recently tried the STP Diesel Fuel Additive Treatment Bundle, which includes the Diesel Injector Cleaner and Ultra 5-in-1 Diesel System Cleaner. Bought it hoping to give my diesel engine a little refresh—maybe clean out some gunk, boost efficiency, or smooth things out. I followed the instructions: dumped the treatment into a full tank and drove it down to about 1/4 left before refueling again. Performance Observations: Smoother Acceleration: Noticed the biggest improvement here. Throttle response felt a touch more refined, especially when accelerating from lower speeds. No more minor hesitations or rough surges—just steady, smooth power. Low-RPM Improvement: The engine also seemed happier at lower RPMs—less grumbly when idling or cruising in traffic. No miracle transformation, but a subtle uptick in responsiveness. MPG? Nope: Unfortunately, didn’t see any measurable increase in fuel economy (which was my main hope). Maybe over multiple treatments? Or my expectations were too high. Subtle Changes: If you're expecting a night-and-day difference, this isn’t it. The improvements were there but minor—worth it if you’re after maintenance, not a power overhaul. No MPG Boost: A bummer, since cleaner systems should help efficiency. Maybe mileage varies depending on the engine’s condition. Final Verdict: Solid for routine maintenance, especially if your diesel’s feeling a bit sluggish. It delivered on smoothing things out and added a hint of pep, but don’t expect drastic fuel savings. If you’re proactive about injector health, this is a good preventative product—just temper expectations for instant miracles. Rating: 3.5/5 – Does its job, but won’t blow your mind. (Would’ve been 4 with even a tiny MPG bump!) Made in the UK for anyone who cares about origin—no complaints on quality there.