I went to school on this stuff.
Basically, oil has different base stock levels. 1 being the lowest, 5 being the highest. Most conventional oils are 1,2. "synthetics" 3-4, rarely 5. Yamaha has a full synthetic oil (base stock 5) that they have used-and tested-in the YZF-R1M. I saw the results on the dyno. They achieved about 5 more HP using the full synthetic oil. The downside is that this high grade oil is about $20/quart, AND it doesn't last long. After doing an oil analysis, it was determined-at least 3 times-that it was breaking down far faster than the conventional semi-synthetic Yamalube 4 10w50 was, which is what, $7 a quart?
I have used all major brands of oil, and all major types. Including Kubota 15w40, which I use in the 2003 F250 pickup (7.3). In the winter I switch to Rotella T6 5w40, because the HUEI injection seems to "like" the lighter oil. When I say "like", I mean it's not as cold natured. Zero MPG improvement. I get the stuff cheaper than most so that is really the only reason I use the T6 over Kubota's 5w40, or anyone else's.
In my drag car, I am finding that Yamalube's full synthetic is a little more consistent as far as MPH and elapsed times are concerned, and honestly a tiny bit faster on the drag strip. But an engine oil analysis was done and it was completely "worn out" by ONE race meet (sheared, vis broken down). I notice a 5 hp increase or decrease on the drag strip becuase I'm bracket racing....where thousandths of a second make a big difference. We went back to Kubota 15w40, as it's cheap, and it's viscosity doesn't break down nearly as quickly. Lost about .02 to .03 second, but we aren't chasing ET or MPH...just trying to stay consistent.
99% of "full synthetic" oils on the market are marketed incorrectly. Meaning Mobil 1, Rotella, etc. Most of the stuff you can buy at parts stores. Brad Penn is a good one, but it's hard to find locally, at least around here.
In a car/truck, yes, perhaps the extra cost of syn could benefit in the long run, say, 150,000 miles of running it. Perhaps it could offset the cost difference in MPG and less frequent oil changes. On a tractor, I doubt there is much difference in cost unless it would be a commercial type equipment that gets used day in and day out. Kind of like comparing 3/4 and 1 ton pickups, gas vs diesel. You pay out the nose for the diesel, pay more for maintenance, upkeep, and repairs....and in the long run they say it pays for itself. It does not, for most average American peiple UNLESS they're using it daily. Diesel 1/2, 3/4, and 1 ton pickups are nothing more than a temporary ego boost, considering that a gas burner will do the same thing with less cost to the average user.
Every vehicle I've owned, I've tried syn oil...and twice have I noticed any difference. One being the race car, the other being my F250, as I have already addressed.
And thus, my experience still says that yes, it is a waste of money for 99% of us.
