OK, so rather than just guessing, I ran the whole exercise again.
Comparing the two oils, yes, Amsoil beats Mobil 1 on VI, Flashpoint, and pour point, but both oils are superior to anything else I found data for. (Remember we're also trying to stay close to the same price point.) Enough said about that.
According to the Amsoil website, their 5W-30 is $5.85/quart. Take that times 6 (if you don't know why, search) and add shipping and it comes to $41.80 per oil change. The 5-quart Mobil 1 jug, plus an extra quart, plus tax, comes to about $26, locally.
Now, the argument is that because Amsoil can be changed less frequently, it's actually cheaper. That's true for some. Is it true for me?
Amsoil's recommended change interval is 25,000 miles, or once a year. As I said earlier, my yearly average is only 8,000 miles. That translates to a Mobil 1 oil change about every 7 or 8 months. If I start with an oil change in January of 2004, and run the intervals and costs out on both oils as far as the year 2027, the Mobil 1 is still cheaper by about $40 dollars. (By then I'll be 60, and my Contour will have about 250,000 miles.)
Now, $40 may not seem like much, and you could argue that it's worth more than $40 just to do fewer oil changes. But in the here and now, time and sweat are cheap, and money is tight.
Of course, all of this is based on current prices and car usage. If anything changes, I'll have to reexamine. And in 24 years, a lot can change.
