Marvel Mystery Oil 50665 Ultimate Fuel and Motor Treatment, 12. Fluid Ounces

Marvel Mystery Fuel treatment is a good way to keep a vehicles fuel system clean. I highly recommend it for vehicles with GDI (gas direct injection) engines. When I first used it in my 2019 Hyundai Tucson, the engine idle seemed rough, but smoothed out after about 200 miles. A mechanic recommended to also fill up with ethanol free gasoline when I added the fuel treatment. Fuel economy dropped about two mpg also with the fuel treatment and ethanol free fuel. I was told that this was normal and was a result of everything being cleaned out of the fuel system. When I gassed after 350 miles, the engine ran much smoother and fuel economy increased substantially. The idle was very smooth as was performance. I now use it in my Ford Ranger as well with even better results.

I got this to use in my Jeep Renegade and after using a couple bottles of it I could tell a difference in how the engine runs. So much quieter and runs a lot smoother. If I could find more to order I definitely would be using this in all of my vehicles. Just wish this was still being made.

Not sure if it helped with anything but I'm assuming so. It had a nice potency to it that I would safely say did some cleaning. My car is 23 years old so I wasn't expecting a dramatic difference.

Used this in my 2013 Jetta SportWagen TDI (one of the ones that sat in a Cali lot for almost 3 years!), was hesitant because of some reviews online saying it would increase the ppm of the diesel but it clearly says right on the bottle “Complies with the federal ultra-low sulfur content requirements for use in diesel motor vehicles and non-road engines.”Will update my review if I notice anything changes.

Mileage went down by 3 mpg after use. If that is something that’s supposed to happen; great. However, I don’t think I want to use a product that decreases my MPG even if for the sake of cleaning out the engine.

I have always used original MMO,great product that is useful for tons of automotive and household applications.I had great results using this product in tank for gasoline at the suggested doseage in my B6 Audi A4 3.0 Quattro.Smoother idle and slight MPG improvement.I will use this product in the fuel tank and the original in oil when need be.

Using this stuff is essential for a good motor. 215k miles on my SUV and still passes California smog.

This new marvel mystery oil is a better fuel cleaner and engine cleaner, it cleaned my injectors good, and my engine was cleaner after i ran it 2500 miles