It is fine. All motor oils are miscible with each other and mixing two or more is not a problem. If you think about it, any time the oil brand / weight is changed the oil is always mixed with what was left in the engine and transmission anyway. And both Rotella oils are great lubricants. I use Rotella 15W- 40 (that is mineral oil, the other is 'left handed' synthetic oil) and always mix in at least a quart of Penzoil 10W-40 just because the bike shifts so much better with Penzoil (but not for very long if only Penzoil is used alone IME).
Other than using an incredibly incorrect weight (straight weight 70W oil in Alaska for example), all modern motor oils are excellent and all work well. Get even reasonably close to the correct weight for the climate and any oil widely available will be a fine choice.
Brian
OK, so this isn't a regular oil thread. Don't worry. I goofed and just wanted assurance all will be well. OK, so I have always used Mobil 1, but on this 2008, I am going economical. So, last change I used Rotella T6... loved it. Bike shifts smoother than anything I can remember. So decided to go again. Got a quart of it and then searched Walmart for a gallon.. which was hard to find.. only a few left.. grabbed one. Today, I get to changing oil. Drained, add a K&N, then start pouring the T6. About a quart in, I see it is 15w40 T6. NEVER even knew they made this.. only had seen 5w40. Well, I got no car, and I gotta get oil in there. So, I add a quart of T6 5w40 and then top off with the 15w40 T6. So, it's kinda CLOSE to a 10w40, right? I am in FL and in a month taking the bike to New Mexico and back so will be changing it again after that trip. Wanted to make sure I'm ok.. I believe I am but want a calm hand of assurance on my shoulder. Tell me I'm right! Please
