I'm NOT posting this just to stir up trouble, I am really curious about people thoughts on this: Back in the mid-1970's, both Mobil and Amsoil came out with high-quality, 100% synthetic oils that could survive long drains, even on the engines of the day. They both advertised their oil as being 25,000 mile oils, and from peoples memories and experiences here, it seems that the oils did survive this service in many cars. But there were some problems with dino-sludged engines of the day having problems with these new high-tech oils. Amsoils response was to bring out a flush to change engines over to their product, but they stuck by their claim that the oil was designed to be used for 25,000 miles. Mobil, on the other hand, recommended people start following manufacturers recommended change intervals, which was often 3,000 miles, or at lest a lot less than 25k miles. So even though Mobil was still making a high-quality oil that could survive 25,000 miles; they were getting people to change it ridiculously early to avoid problems. People got amzing results changing this high-quality oil frequently, and more importantly, Mobile made a lot of money off this arrangement, and became the name in synthetic oils. Amsoil is still a respected name in synthetic oil, but because they stuck to the fact that their oil would last for 25,000 miles, instead of catering to the prevailing 3k mentality, they are a much smaller comapany. Amsoil and Mobil still make high-quality synthetic oils, and tests have shown that they are fairly equal in performance and service life. Amsoil still claims their oils are good for 25k, and even 35k in some cases. Mobil, on the other hand, has only recently started to claim its 'EP' oil is good to 15k miles. So Mobil is making massive amounts of money from people who change their products anywhere from 3k to 15k miles; when both products could probably go at least 20k, if not 25k, just like Amsoil. I know that Mobil is somewhat cheaper than Amsoil, but not cheaper enough to cover this blatent rip-off. People on this site rant and rave about Castrol, and how it is 'ripping people off' by charging synthetic prices for a group III hydrocrack and making huge amounts of money doing it. Buy why, oh why, is no-one just as mad at Mobil for making a fortune over the past 25 or so years for getting people to change a perfectly good synthetic oil early, when all along they could have stuck to their 25,000 mile claim, like Amsoil has for all these years? Just seems to me like a bit of hypocrisy.....! Please note - I am not a Mobile hater. Have no experience with their products. This is just an observation of the situation from the 1970's to the present.