Quite costlier as well because its synthetic. ZIC 4t is the most low quality synthetic(im using in my new gs but it hasnt caused any problems). LM is more likely to be a true synthetic oil so it will be expensive.
BTW if you're interested in tuning yourself give this guide a read
Tuning Yamaha FZ 16 Carburetor
its for GS carb but the principle is same for any bike