Rotella T 15w40 OK?

[ABerns]

Hi, all -

I have a 1984 Honda CB700SC (Nighthawk 700S). It has an air/oil-cooled inline 4. For the past few years, I've been using Rotella 5w40 synthetic (not T6, still using an old stash). I've been reading a lot about shear, so I was thinking of switching to 15w40. HOWEVER, I'm worried that as an air-cooled motor, the synthetic may provide better protection with the heat (not sure if heat is even an issue in anything besides the V-twin air-cooled...)

Also, any time I am cruising for more than 10 minutes at 70+ MPH, oil consumption is very noticeable - on the order of half a quart per 300 miles or so. At speeds below 70, there is NO oil consumption. I'm wondering if perhaps the oil consumption is coming because of the 5w40 shearing? Unfortunately, I didn't drive too many interstate miles after my oil change, so I can't comment on if consumption increases as the miles on the oil increases.

So, I guess I have 2 questions:

1) Can the conventional 15w40 Rotella provide the same protection in an air-cooled inline 4 as the 5w40 synthetic (ignoring cold starts, I usually take long trips and take things easy until it warms up)?

2) Would the switch to 15w40 perhaps cure the oil consumption issues I've been having?

Thanks!
Andy

Edit: The manual calls for a 10w40 for my operating range, so T5 would work, too. I just don't hear much about it here...

 

[dwendt44]

Conventional Rotella (15W-40) is fine. Does the 700 have an oil cooler?
The T6 would allow a longer oil change interval, but the white jug oil should work fine for you.
Don't think 'shear' in and of itself will affect oil consumption;
Oil consumption only at higher rpm sounds like something engine related, not oil itself.(rings?)

 

[ABerns]

Thanks for the reply! The 700 does have an oil cooler. I don't mind spending a little bit extra on oil, considering it only gets a few changes a year. So T6 would be a better choice for protection?

I keep hearing how the 5w40 will shear more than the 15w40, but with the new formula, I think I'll give that a shot. Especially considering the oil consumption is unrelated.

 

[RWEST]

Either version has its adherents. I can't imagine going wrong with either one. Might be worth a try to see if the 15-40 will help the oil usage issue. If you try that, post up the results, k?

Tractor Supply Co. carries the Rotella T Synthetic 10w40 around here. My brother put that in his Gold Wing last change and loves it. Says his bike shifts much better than before (Honda GN4, I think was what we drained out of there).

 

[grampi]

Syns are better than dinos, but the Rotella seems to be a very good dino...

 

[sunruh]

Originally Posted By: grampi
Syns are better than dinos, but the Rotella seems to be a very good dino...


i doubt you have any proof to back that up.

i have proof that disagrees.

 

[ABerns]

Sunruh, would you recommend giving the 15w40 a try then? The fact that I have an oil-cooled engine won't cause too much heat for a dino, right?

I wouldn't mind trying it, since I hear the 15w40 resists shear more. Took me a while to wrap my head around how a "synthetic" can shear more than a dino, but then I found some posts on Group III vs. Group IV vs. Group V, and I see that the 5w40 still needs VII to get to 40. Previously I've been told all synthetics don't shear hardly at all, since very few if any VII are needed. The myths that one encounters...

 

[heavyhitter]

Your Nighthawk will run just fine on 15w40. That bike will not create more heat than the oil can handle. Even if you are running lean that oil will be enough for your application.

 

[sunruh]

Aberns,

i think any of the hdeo would do great in your old bike.

which probably spells out an SG oil in its manual.

consumption can come about multiple ways. will the thicker oil solve it? hard to say until you try it.

but you will be safe with the hdeos. have no fear. wont harm the clutch.

and dont worry about cold flow startup. i see you are in iowa, not like you are riding in the winter now are you? ha ha ha.

 

[dwendt44]

Most 15W and 20W are good down to 0° at least. If you ride in that temp., good luck!

 

[ABerns]

Gonna drag up this old thread again for some closing statements. I switched to Rotella T 15w40. I can't tell any major differences from the Rotella 5w40.

Anyway, the oil consumption issue is still present - switching to the 15w40 made no difference. So, I guess my hypothesis of the oil shearing down and then burning was false. Either way, now I have a nice cheap solid oil to use!