5w40 vs. 10w40

That was my initial feeling too. I like doing everything by the book so I don't really like the idea of 5w40, but that's all I saw that oil offered in. With that being said - is there any other full synthetic 10w40 that's around the same price as the Rotella T6 that you know of? 

Yea, can't go wrong with what Evitzee said. Oil has been engineered in such a way that as long as you change it in regular intervals and use what is recommended, you should not be having issues where $20 Motul 300 is a better option than $5 Rotella FOR THE AVERAGE RIDER.

I personally run Mobile 4T racing and I only run that because I ride exclusively track and canyon in desert environments. So I'm someone who pushes my bikes constantly to redline, at higher engine and ambient temps, so I spend the $10 or $12 a bottle. For most, that's overkill. Go with what falls within the recomendations at a good cost if you're not pushing the bike hard in extreme hot or cold temps.

I know you just joined the forum so you weren't here for that, but only about a week or two ago we had a good discussion about all of this. Probably one of the most civil discussions I've ever seen about this topic on a forum. Hahahahaha

fz10.org/thread/1833/type-oil

Just make sure it is JASO MA certified for wet clutch transmissions, I'm not familiar with any Valvoline motorcycle oil.  You cannot use regular car oil, it will mess up your clutch plates and make them slip.  Not good.

Oh yes. I confirmed that   I think it's JASO MA2

Yes T6 is JASO MA. If you use the Yamaha brand oil and filter and resister it on there site every oil change you can get the 20yr engine warranty. I’m running there 15/50 synthetic 

Thank you for that info. But 2 questions. First on the T6. It's JASO MA (I don't think Yamaha asks for JASO MA2), so good. But Yamaha specifically prohibits CD oils (page 7-12 of the European owner's manual on .pdf), which I believe all diesel oils must carry. Is that the case with the T6? If it's not CD, then I might consider it, since I prefer 5/40 than 10/40. But if it's CD, then no way I'd use it, especially under warranty. Now my second question: I didn't know Yamaha extended the engine warranty if you use their oil, but is that in the US too? Never heard of that before, but will look into that. Thanks brother.

It's restrictive in that you have to adhere to the time and mileage specs in the Owner's Manual.....that means changing oil every six months regardless of mileage, a waste of time and expensive Full Synthetic Yamalube oil unless you do at least 4,000 miles every six months. For a street rider it is a gimmick, and an expensive one at that. Never had a m/c engine have a lubrication issue or engine failure.....don't expect the FZ-10 engine to be any different. I looked at it when I first got the bike and said 'pass' when I saw what the owner had to do. To me it is a sales gimmick.

Checked the Rotella T6 at Walmart, and it's not CD, like the manual prohibits. It meets API CK-4, CJ-4, CI-4, AND CH-4. And several 'performance requirements', including JASO MA/MA2. Most motorcycle and car oils meet API Sx specs, but manual doesn't say anything about either Sx or Cx specs; just JASO MA/MA2, so seems like the T6 should be fine. As far as 5/40 vs 10/40, there's absolutely no disadvantage of using 5/40; on the contrary. It flows better when cold (thinner), so your engine starts getting lubricated quicker than with 10/40. You should never rev a cold engine hard, due to oil being too thick to lubricate the engine properly, but a 5/40 oil is less thick than a 10/40 when cold, so that's always a plus. When hot, which is the ultra great majority of the time the engine is run, is what matters the most, and both are 40, so no issues. Yes, manual also allows 50, but I'd only use it if bike is tracked. A thicker oil is harder to pump, especially at higher rpm, again, lubricating less than ideally. I'd stick with 40 (5/40 or 10/40), and unless your engine is consuming oil, stick with that. Even at high temperatures (I live in hot TX), your engine doesn't really need 50 weight unless run hard most of the time. But to each his own, of course. As a final comment, it's never okay to go from 5/40 to 10/40, for instance. But from 10/40 to 5/40, zero issues. In fact, most manufacturers are starting to recommend 0/x oils for every application. I noticed Mobil1 started making 0/30, and that's exactly what I bought for my new F-150 Platinum twin-turbo, and the cold start engine noises that my truck had since day 1, disappeared 100% after the 3K-mile oil change. Nice. Porsche has recommended 0/40 for some time now, and other high-performance brands are following suit. And oil manufacturers clearly say their 0/x oils are recommended to substitute 5/x, 10/x, etc oils, so you don't have to take it from me. He he. Anyway, I've heard of people using Rotella T6 for years and years, but was always skeptical of diesel oil on a high-performance motorcycle engine, but will try it this time, and see what happens. The main reason I want to try it is my bike seems to struggle to start when cold, even though it hasn't been cold, and with a fully charged battery. Bike starts, but not like on most vehicles, where engine immediately goes to 1,400 rpm, or whatever. It doesn't quite hard-strats, but close. It starts at less than 1K rpm, struggling a litte bit, then it shoots to high idle, and goes down normally after that. Hopefully with thinner oil it'll struggle less, especially when colder. For some reason, this is a very typical bike behavior, for some reason. Most of my BMWs also struggle to start, especially when cold. Below 50º, many times they stalled, and had to try again, the second time starting normally. Almost like if they were carbureted, and you forgot to hit the throttle for the high-idle cam to push under the throttle stop. Remember those days? Ha ha.

Ah, it's springtime and time to start talking oils again.