I purchased this product a little over a month ago to use it on my next Oil Change in my 2007 5.7 liter Toyota Tundra with 390000 plus miles. I have used synthetic 0w 20 mobile 1 motor oil in it probably since it got over a hundred thousand miles. Over the past six months or so my engine started making a lot of racket under the hood with what seems to be a timing chain with a loose tensioner. At least that is my diagnosis based on other YouTube videos I have found with the same exact noise. It usually will quiet down once the engine warms up, but recently even that wasn't helping the sound go away so I started looking on the web for oil treatments because it just didn't seem like a normal oil change was doing the trick and looking for a possible cheaper fix because tearing apart the engine to inspect the timing chain would be at least $1,000 if not $2000 or more from a dealer. In addition to adding 9 oz of Archoil into my motor oil since that is what it recommends at 1.2 ounces per quart of oil for gasoline engines, I also decided to use 5 W 20 Mobil 1 extended range high mileage full synthetic oil in this oil change. I'm going on a little over a week now and there is no more clicking or excessive noise going on under the hood. In addition, I usually change the oil every 10,000 Miles when I use the extended-range Mobil 1 motor oil, but this last change I decided to do it early since I wanted to try Archoil out faster and change the oil at 7,000 miles. The oil was super black and now realize that it may be a good idea to start changing the oil at lower mileage intervals because the high mileage extended range motor oil to me is not going to last 20,000 miles as suggested on it's label. So going forward I will most likely start changing the oil in 5000 mile increments too just because I think it will be better on the engine and if this does keep the noise down under the hood it can only be good and give me more peace of mind. As for mileage (mpg) improvement, I have seen a little improvement. However, after an oil change I tend to see a little improvement anyways, but my Tundra on the highway is getting 20.3 miles per gallon this cool morning after driving about 35 miles with two stops along the way as I drove to work, but by the end of the day after it was averaging 18.5 by the time I got home. I wish I could say the same though for city driving, but city driving is worse and usually it brings that average down to 16 to 17 miles per gallon once I have driven on a full tank of gas. Regardless, I think those numbers are pretty good for a 2007 Tundra with over three hundred ninety thousand miles on it (see Odometer picture). If I could have any recommendations for Archoil on improvements for this product it would be to have 18 or 20 oz per bottle instead of 16, because a typical gasoline truck is going to have about eight quarts of oil in it and doing their math that will put you a little short when the next Oil Change comes around to be able to use a bottle on two oil changes. In addition, they really need to have a better View gauge on the side of the bottle with ounce markings for those of us that do not use an entire bottle in one oil change. Overall though I do believe this product has helped quiet my engine down dramatically and has improved gas mileage a little. I have attached a video that I took of my engine back in February 2021 when I first turned it on and the noise was really bad, then a few minutes later after it warmed up and the sound got a little better, then the last 10 seconds or so is after running Archoil through my engine after roughly 300 miles of driving and after the new oil change which I just did on May 16, 2021. The video speaks for itself and I can't guarantee it will do the same for you, but I'm a believer that it helped quiet down my engine dramatically. I hope this review helps someone, and hopefully it will do the same for you.Update: April 11, 2022.I've used Archoil now on several oil changes and it continues to do it's job and keep my engine noise down significantly. My engine will start "acting up" around 5,000 to 7,000 by the noise returning more frequently and know it is time for another oil/Archoil change. I've been very pleased overall and even though this is expensive I believe it is saving me a lot more than a costly repair. My Tundra now has over 414,000 miles on it and still going strong.