I put a bottle in my 200 Honda Accord V6, with 235,000 miles on the original engine, and yes, it had a noticeable affect, it was quieter, smoother, the engine on cold starts so much quieter and smoother too, had no effect on the VTECH system, thing would still haul up to the speed limiter, So I then put a bottle in 1997 Suzuki sidekick, same again so much smoother, and same again, cold starts are so smoother.

On all three cars, the gas mileage as increased, on average around 3 to 5 mpg.

I know own a 2017 Kia optima, these engines are kinda noisy from new, it as 18,000 miles on it, so I thought, what the heck, next oil change, I will add this, you could hear the engine quieten down and smooth out before the bottle was empty, I always pour it into a warm running engine, stops oil pump shock.

It helps a little with cold start tick, but not a magic fix. It is much thicker than I expected, a turbo/ smaller engine might consider a different product. I have not seen fuel economy improvement. My old Ford 4.6 does not use much oil, and still doesn't, so Hyperlube does not hurt an older engine. I have not tested in winter weather to see how it flows in colder weather. Neutral opinion, but will not repeat purchase.
UPDATE: I had the oil changed at a shop, as I also wanted the steering components looked at. Even with putting the gas pedal to the floor to delay starting, so the oil can reach the top of the engine. There is a dry knock much longer, and a delay for oil pressure to register. I will have to drain off a quart of oil, and place more hyper lube. Hyper lube is great for my frequent short trips, and works better than originally thought.

I was first introduced to Hyperlube 23 years ago. A farmer told me about it. He had been using in all his pickups and tractors for 30 years before that. I have since used it in everything from motorcycles to lawnmowers. Never had a motor failure. For at least 10 years I have been only using synthetic oil as well for all my motors. Wish it worked for transmissions. Might also be great with peanut butter on english muffins ;-D

I have been changing oil a LONG TIME and have used many products including LUCAS, STP, etc. and from now on it is this product in the motor. I have two Buicks with the 3.8 V6 Series 2 engines among 4 other vehicles. Now, these motors are good engines but they tend to be a bit "thrashy" for lack of a better word. They sound like sewing machines at start up and quiet down a bit when warmed up. This Hy-Per Lube product seems to dissipate some of the start up and run "sewing machine" noise. The engines are definitely quieter. I only use synthetic oils and Royal Purple filters so the change in engine noise is attributable to this product. I only write reviews that are honest in nature and have no manufacture affiliation with Hy-Per Lube. I believe you will not be disappointed with the product however it is not to be used to refrain from regular oil changes. It is a perfect fantasy believing one can drive with "extended life" motor oils for longer than recommended changes but engine heat and weather conditions dispel that myth.

Great for 6 quart gm oil changes. Five quart jug of oil and one quart of hyper.