Spark Plugs - NGK DPR8EA9 (These are standard plugs and what the current NGK website says to use which kind of surprised me since it's the same plug they recommended 30 years ago. Also, I had a 2nd gen Miata with the "wasted spark" design and I tried the Iridium plugs which I found were overkill and offered no advantage - the standard plugs ran just as well at a fraction of the price. I use NGK in everything, cars, mowers, weed eater, leaf blower, etc. I also like the fact that no anti-seize is necessary with the proprietary coating.)
Oil - AMSOIL 10W/40 Metric Motorcycle Oil
Oil Filter - NAPA Gold 1358 (made by WIX)
Coolant - Honda Long Life (same as the Honda motorcycle coolant but in a bigger jug at a cheaper price.
Gas - Top Tier (Citgo, Exxon or BP) for long trips and Citgo non-ethanol which I keep in a jug in the garage for my day trips. I use mid-grade 90 octane which is probably overkill but that is all I can get in the non-ethanol, so I stay with that octane. I try to never use non-brand gasoline.
I'm kind of OCD. Every time I put my Shadow on the jack, which is pretty often, I check the oil level, coolant level, chain slack and lube (Chain Saver Spray for chains with o-rings). And I look for the possible leaks. So far, no problems anywhere.