People need to understand about motor oil to make the decision on what is right for them including if Royal Purple is what they should use or not.  Forget the marketing, and anything else that suggests this or any oil will do anything "spectacular".  What it can do is what a good motor oil can do, lubricate and help protect an engine from wear (when combined with a good filter). The synthetic oils benefits occur most when an engine is subjected to the extremes, high RPM, high stress, high/low temp situations where it will remain effective better than a conventional oil. Synthetic oils may also maintain their original properties a while longer than conventional oils.  That is it however. That is very important stuff, what motor oil is for. That is good enough, all that should be expected. But it is still motor oil. Any claims of this or any other oil making your car go faster or get better MPG or anything like that should not be believed. That is not the job of motor oil.The definition of "synthetic oil" in this Country is vague and most oils labeled "fully synthetic" are not made from 100% synthetic base stocks. To find out more about how this works look up Mobil Vs Castrol, this was the lawsuit in this country that allowed oils that originated from dino oil to legally be called "fully synthetic".  This does not mean they are bad oils, just that the use of the work synthetic can be misleading.One would need to look to see what base stocks are used to see just how fully synthetic an oil truly is. The base stocks in motor oil are Group I,II,III,IV and V base stocks. Group I-III (1-3) are all conventional mineral oils that have come from the ground. Dino oil. Only Group IV and V use synthetic base stocks (P.A.O. for group IV) and (Esters for group V).95% of oils labeled "fully synthetic" actually begin with group III base stocks which are then highly processed in to the final product.This does not mean that an oil is bad because it is not a true "fully synthetic" oil using 100% group IV or V base stocks or better just because it does use them, but this is something I think is misleading and not understood by most. Though being a true group IV oil using those P.A.O. base stocks is considered better by many. It is an indication of a high quality oil, and certainly meets the definition of a true fully synthetic oil, just not the only consideration.There is much more to an oil than just the base stocks used. The formulations are very complex including many additives with detergent and anti-wear properties along with several others. Many factors go in to making a top quality motor oil.I would not suggest one think they can go incredibly long times between oil changes just because they are using a high quality oil or because a certain mileage figure is on the label. When used with a good filter one may be able to go longer between changes with a good oil, but to protect your engine better you also need to keep clean and fresh enough oil of any type in it. This oil is no exception. Your oil may be capable of outlasting your filter. Some find that changing filters more often than their oil helps extend change intervals. Also there is more to consider when determining oil change intervals than just mileage. Engine type (does it have a turbo for example), environmental extremes etc. also need to be considered. And time is a consideration too because while the oil itself may not be "worn out" or the additive package in it may still be effective (particularly in Extended Performance versions which contain larger amounts) still there are contaminants that oil filters do not remove which are a result of the combustion process, over time these build up and can only be removed by changing your oil. This is also why if you use a vehicle seasonally such as storing your motorcycle over the winter it is best to change the oil when you put it away rather than at the start of the season.If you look on the bottles of oils with claims they can go for long periods of time between oil changes (15K plus) you will find some small print saying things such as "Do not alter oil change intervals from manufacturer requirements on vehicles under warranty (as this will likely VOID your warranty not keeping the maintenance schedule)" and "25,000 miles OR ONE YEAR" as well as many other various conditional statements about the vehicle operating conditions. What may be OK under ideal and perfect conditions is different from most all real situations.Some people engage in oil testing, sending their oil to labs to find out condition of the oil.  For me this seems perhaps reasonable if one it attempting to find out what length change interval they are able to obtain with a certain oil/filter combination.  However as something done on a regular basis for the average consumer this costs as much as an oil change so I would just change the oil instead of finding out the condition the old oil is in.As to Royal Purple being a good synthetic oil? I would say yes it is. Also very expensive particularly with this deal. If it is either the best or worth the price is the larger questions to consider. Is it worth it at this price? I would say NO it was recently on sale for 6.99/quart, at that time or the next time it goes on sale that is the prime time to purchase. Personally I prefer other brands, though my decisions are changing along with the changing of formulations of the oils I use. One should do research in to various synthetic motor oils and consider those as well and decide which one to use. Do not go by marketing claims. There are independent tests and discussions, there is even one with over 1000 posts on this subject on Amazon right now. Many other outside oil forums as well. One can also have their oil tested to compare results vs other brands used at various intervals in their own vehicle if one wants to do that sort of personal research which will yield at least some results.  Also formulations are constantly changing so what ingredients used in any particular oil one year may not be what the formulation is today or will be tomorrow. If you research oil and decide that it is worth paying a bit more for a true group IV oil, then that is a reasonable decision to pay a bit more for that oil. I believe this RP is among Group IV oils, meaning it uses 100% synthetic base stocks.  But contact Royal Purple to confirm this because their formulations change like all others. Make sure you know what you are buying.I would also encourage purchasing any oil when it is on a big sale or has a rebate etc.. I believe most synthetics are overpriced and should be purchased only when on sale as this does happen on a regular basis. Check Amazon and other auto supply stores. There are constantly sales on synthetic oils and/or rebates making the cost per quart 6.00 or less on a regular basis, this is the time to purchase your oil.  Often there are packages with filters which can be good deals as long as the filter is the one you would like to use also.  This nor any other oil will perform well without also using a high quality filter, period. Make sure you are also using a high quality filter. The two need to both be of good quality for best performance and protection.I give this a 4 star rating due to price. It has been on sale for less recently and that is the time to purchase expensive oils. Plan ahead and buy your oil when on a really good sale. You can save about 50% or at least close to it often times especially when offered with packages including an oil filter (as long as it is a good filter). The star rating reflects the value of this deal at this price.In the end get a high quality oil but remember no oil is going to be providing its full benefits if it is no longer effective due to excessive use or age.  Keep your maintenance schedules up to get the best performance and longest life out of your vehicle.Royal Purple IS one in the group of top quality motor oils, just where it ranks is much more difficult to determine.  Disregard outrageous claims made by any manufacturer or person and do your own research in to various synthetic oils to make a decision on which to use.  There are several very good quality brands. Also learn about API, ILSAC and Dexos1 specifications mean. This Royal Purple DOES meet the most current API specification (SF) the ILSAC GF-5 and GM's new Dexos1 requirements. It should be compared against other synthetics that also meet those same specifications. THOSE ARE IMPORTANT RATINGS. These are your best street car motor oils. So YES this is a good oil, NO it will not do anything other high quality synthetic oils in the same class can do, and No this is not the best price I have seen for this oil.Instead of comparing claims on a bottle (other than those API, ILSAC and perhaps Dexos1 ratings) do some outside research. Ignore outrageous claims and make an informed decision based upon knowledge of the oil and filters you purchase and what an appropriate price to purchase them at is.EDIT: Note that at the time of the review Royal Purple was using PAO base stocks.  I have information that it is not not a 100% PAO oil. This has been a pattern among oils that were once 100% PAO group IV oils so you can not count on any brand maintaining their formulations or advising or a new formulation or change.  There are some advantages to a PAO oil such as no need for V.I. additives and if you believe in the value of P.A.O. base stock oils that could justify a slightly higher purchase price.  My belief in this change is a response to this question by a representative or Royal Purple.  This does not mean it is no longer a good oil to buy just that the formulation may no longer use P.A.O. base stocks.  One should know what they are paying for particularly if they are purchasing a product at a premium price especially if that product no longer uses the ingredients one things it does.