That's right. I run synthetics in mine too - Except the engine and transmission. Weird, huh? But I change oil a whole lot in the engine and tranny - I am a big believer in fresh oil. And synthetics are too high in cost at that frequency. And I still prefer 30w in the summer and 10/30 in the winter.
But the rest of it - Transfer case, differentials, and transmission, if it's a stick... All the 90w places are all synth. Now that I ain't burying the thing in mud or in the river every other weekend, that stuff doesn't get changed as much (or rather, nearly at all), so synth is worth the money.
And I am a big fan of Kendall Super Blue for grease. When I was in lawn care, I got sold on that. Nothing else comes close to that super blue staying in the timken rotors on mowing machines, which is about as punishing an environment as you will find.
I bite the bullet and run synthetic in the engines, too. When it hits -30 and you can't plug it in but have to go, it's gratifying (even though I cringe a bit and hate to do it) to have that engine start.
But I have tried to pour 30W (mineral oil, not synthetic) at 30 below, and it doesn't. I am a firm believer in oil changes every 3,000 miles, too.
Yes, it's expensive, and in theory that oil is good for 5,000 miles or more, but I was told by a wise old shadetree mechanic that the long chain hydrocarbons in motor oil tend to break down with stress, and my reading confirms that. Besides, if it's anything but honey colored, its carrying a load of particulates around the engine, and that can't be good.
I think it works, because I have a rebuilt carbureted engine that has over 120,000 miles on the rebuild. Dropped the break in oil at 500 miles (drove down to Casper, WY, on my way to a well in Nevada and changed the oil in the K Mart parking lot), ran regular 30W Castrol for the next 2500 miles, and went to Syntec for the winter when I got home. The long trip for the break in run didn't hurt, either, but the longest that engine went between oil changes was about 3500 miles, and it will still fire today.