Sidekick
Save Ukraine Stop War!
I'm considering switching from Rotella 15W-40 to 5W-40. Would this be a wise choice? Any input or recommendations would be appreciated.
Question about Rotella 5W40
- Thread starter Sidekick
- Start date
Go for it. I have been using Rotella 5W-40 in my Gold Wing, KLR, and two quads for years. Never a problem.
Why are you considering the switch?
Agreed (with MidLife). 15W- is already thin enough for any cold-weather riding.
Last edited:
While I will probably get flamed for saying anything bad about oil that folks have used for years, however, with that said, let me share something with you about my findings.
I’ve done UOA’s (several) on both versions of the Rotella oils over the years, on many different bikes.
I also used it several years ago when it was a different formula with fair results.
Mobil delvac 1300, chevron delo 400, and valvoline premium blue always had better numbers in the UOA’s etc.
However recently I have replaced several clutch packs in 2016 police and civilian model bikes that were using the NEW version of this oil. YMMV (use at your own risk)
I have done a NON-Scientific test a couple times with the same results which turned me away from using 5w40 oils in these bikes now.
Two identical ST1300’s both 2016 crate bikes, both had approximately 3 oil changes done etc.
Test:
One bike 5w40 other bike 15w40 Dino.
Both bikes placed on table lifts out of service, drained oil, for over an hour (together) put plugs back in, oil filters NOT removed, and left them sit for 3 weeks.
Then pulled drain plugs back out….
15w40 oil drained about 2 oz of oil that drained down while sitting.
5w40 oil drained over a cup full of oil, and spilled on lift table!
Where did this oil come from?
My guess is that it returned to 5 weight fish oil and drained off of all the top end parts etc.
I am more concerned with start up damage without lubrication.
Yes, 5 weight oil flows faster, but it still means it has to get up to the areas that it left when starting (just my opinion).
Test 2:
Tearing down the engines, 15w40 oils still coated top end parts, 5w40 oils left engines void of oil on top ends.
You decide, you pay your dollar and take your chances.
NONE of our service manuals direct us to use 5w weight oils, only people of the internet etc.
And yes, some of those folks who state their bikes ran fine on it were very surprised to see the wear on the engines when torn down.
I’ve done UOA’s (several) on both versions of the Rotella oils over the years, on many different bikes.
I also used it several years ago when it was a different formula with fair results.
Mobil delvac 1300, chevron delo 400, and valvoline premium blue always had better numbers in the UOA’s etc.
However recently I have replaced several clutch packs in 2016 police and civilian model bikes that were using the NEW version of this oil. YMMV (use at your own risk)
I have done a NON-Scientific test a couple times with the same results which turned me away from using 5w40 oils in these bikes now.
Two identical ST1300’s both 2016 crate bikes, both had approximately 3 oil changes done etc.
Test:
One bike 5w40 other bike 15w40 Dino.
Both bikes placed on table lifts out of service, drained oil, for over an hour (together) put plugs back in, oil filters NOT removed, and left them sit for 3 weeks.
Then pulled drain plugs back out….
15w40 oil drained about 2 oz of oil that drained down while sitting.
5w40 oil drained over a cup full of oil, and spilled on lift table!
Where did this oil come from?
My guess is that it returned to 5 weight fish oil and drained off of all the top end parts etc.
I am more concerned with start up damage without lubrication.
Yes, 5 weight oil flows faster, but it still means it has to get up to the areas that it left when starting (just my opinion).
Test 2:
Tearing down the engines, 15w40 oils still coated top end parts, 5w40 oils left engines void of oil on top ends.
You decide, you pay your dollar and take your chances.
NONE of our service manuals direct us to use 5w weight oils, only people of the internet etc.
And yes, some of those folks who state their bikes ran fine on it were very surprised to see the wear on the engines when torn down.
Andrew Shadow
Site Supporter
Debates will rage forever about which type/brand of oil is better. Regardless of how logical opinions may be or how compelling the available evidence is these debates will continue to rage. Because of that I am expressing no opinion on oil type/brand however, the question here is in regards to the viscosity rating not the type of oil.
Insofar as the viscosity rating goes, I never understood why anyone would stray from one of the viscosity ratings that the vehicle manufacturer has specified for a given vehicle. There are many factors that go in to deciding what the best oil viscosity is for a given engine, and many of those factors are variables that change as the engine and the oil temperatures change. In many cases the engine manufacturers don't even decide themselves what the best viscosity oil is for their engine. They send the engine design specifications to lubrication engineers who do nothing but specialize in lubrication chemistry and mediums. These engineers analyze the various design specifications and tolerances of the engine and they tell the engine manufacturer what type and viscosity of oil is best suited for that particular engine under various temperature ranges.
I acknowledge that both of the ST engine designs are pretty old now and were not as highly engineered as modern engines are. I also realize that most motorcycles will not see temperatures as cold as automobiles routinely do so the variances listed above likely have a lesser influence. Having less sophisticated engineering these engines are probably more tolerant of straying from the manufacturers viscosity recommendation than newer engines are. It is also obvious that when they were developed choosing the best oil viscosity was not made with the same level of sophistication as it is now. Regardless of all that the question remains- Why stray from the manufacturers specified viscosity? I am under no illusion that I know something that the engine designers and lubrication engineers don't. I doubt that I have the capacity to competently decide if a viscosity that they do not recommend is not only not harmful to the engine but is actually a good choice. Further complicating the matter is the effect that this choice has on the transmission and clutch as they depend on the same oil but for very different requirements.
People can and will continue to use whatever type and brand of oil that they think is the best. Just about any oil on the market is available in several different viscosity ratings. Amongst those available choices it is unlikely that there isn't one that is specified by the manufacturer. Regardless of the type and brand of oil chosen, the logic of using a viscosity rating that is not specified by the manufacturer escapes me.
Insofar as the viscosity rating goes, I never understood why anyone would stray from one of the viscosity ratings that the vehicle manufacturer has specified for a given vehicle. There are many factors that go in to deciding what the best oil viscosity is for a given engine, and many of those factors are variables that change as the engine and the oil temperatures change. In many cases the engine manufacturers don't even decide themselves what the best viscosity oil is for their engine. They send the engine design specifications to lubrication engineers who do nothing but specialize in lubrication chemistry and mediums. These engineers analyze the various design specifications and tolerances of the engine and they tell the engine manufacturer what type and viscosity of oil is best suited for that particular engine under various temperature ranges.
I acknowledge that both of the ST engine designs are pretty old now and were not as highly engineered as modern engines are. I also realize that most motorcycles will not see temperatures as cold as automobiles routinely do so the variances listed above likely have a lesser influence. Having less sophisticated engineering these engines are probably more tolerant of straying from the manufacturers viscosity recommendation than newer engines are. It is also obvious that when they were developed choosing the best oil viscosity was not made with the same level of sophistication as it is now. Regardless of all that the question remains- Why stray from the manufacturers specified viscosity? I am under no illusion that I know something that the engine designers and lubrication engineers don't. I doubt that I have the capacity to competently decide if a viscosity that they do not recommend is not only not harmful to the engine but is actually a good choice. Further complicating the matter is the effect that this choice has on the transmission and clutch as they depend on the same oil but for very different requirements.
People can and will continue to use whatever type and brand of oil that they think is the best. Just about any oil on the market is available in several different viscosity ratings. Amongst those available choices it is unlikely that there isn't one that is specified by the manufacturer. Regardless of the type and brand of oil chosen, the logic of using a viscosity rating that is not specified by the manufacturer escapes me.
This is an easy one. Desire to use a cheaper oil. Some folks pick up the idea another viscosity/brand is better. Some folks think they know better than the mfr, for whatever reason. Some folks listen to a perceived eggspert on youtube. Take your pick.
In addition, engine wear due to lubrication or insufficient lube takes place very slowly. If an owner sees no engine damage in say, 50k miles, his decision to use cod liver oil to lube his super gofast crotch rocket has no downside. Realistically, how many folks put 50k miles on their bike before they sell it? We have seen a fair number of bikes purchased with UNDER 30k miles (I pulled that number out of the air) that are 20 years old. So, the thinking goes, what is the harm in using sea urchin egg oil?
We have a rather sophisticated, mature, informed group of riders here. Go online to say, the Stromtrooper or other motorcycle forums and check out some of the questions asked there. A lot of the younger riders have no technical background nor years of experience wrenching. I don't fault them for asking the questions, only if they don't do enough research to be able to decide the correct answer for themselves. Believing someone else's opinion to be correct when you don't know his/her background is folly. Curiosity, along with common sense, is draining away from our society.
Last edited:
This is the BEST written response in an oil thread I have read period!
Well said!
@Igofar 's first post above made me do some thinking. 
My logic has always thought that a thinner oil would get picked up quicker to reach all the engine surfaces than a thicker oil would. But I can't explain why more oil drained out with the thinner oil in his experiment.
Other than the initial startup, I doubt it makes much difference in the end. The final viscosity is the same and the engine heat will get it to that point very quickly.
@Andrew Shadow made a good comment also. The tolerances for the ST's engines are not as tight as newer engines are. My XR requires 5W-40 oil. Older engines probably don't. Our first brand new car was a 75 VW Rabbit. I wanted only the best for it, so I put in Mobil 1 oil. I think it was a 5W-20 and the car required a 30 or 40 weight oil. Anyway, one day we're driving down a side road and the traffic light turns red so I hit the brakes. An idiot light on the dash flashes red momentarily. I didn't catch which light, but it got me concerned. A few more blocks down the road and the traffic light turns red. This time I'm looking at the dash. It was the oil light! As luck would have it, a Mobil gas station was on the opposite corner. I pulled in and checked the oil. In a 4 quart system, I put in 2.5 quarts of oil! My conclusion was that the oil was blowing past the rings. At that point, I went back to what the owner's manual recommended and the engine quit using oil.
Now my wife's Prius recommends 0W-20 weight oil. But it is made for that.
Last thought...if it ain't broke, don't fix it.
Chris
My logic has always thought that a thinner oil would get picked up quicker to reach all the engine surfaces than a thicker oil would. But I can't explain why more oil drained out with the thinner oil in his experiment.Other than the initial startup, I doubt it makes much difference in the end. The final viscosity is the same and the engine heat will get it to that point very quickly.
@Andrew Shadow made a good comment also. The tolerances for the ST's engines are not as tight as newer engines are. My XR requires 5W-40 oil. Older engines probably don't. Our first brand new car was a 75 VW Rabbit. I wanted only the best for it, so I put in Mobil 1 oil. I think it was a 5W-20 and the car required a 30 or 40 weight oil. Anyway, one day we're driving down a side road and the traffic light turns red so I hit the brakes. An idiot light on the dash flashes red momentarily. I didn't catch which light, but it got me concerned. A few more blocks down the road and the traffic light turns red. This time I'm looking at the dash. It was the oil light! As luck would have it, a Mobil gas station was on the opposite corner. I pulled in and checked the oil. In a 4 quart system, I put in 2.5 quarts of oil! My conclusion was that the oil was blowing past the rings. At that point, I went back to what the owner's manual recommended and the engine quit using oil.
Now my wife's Prius recommends 0W-20 weight oil. But it is made for that.
Last thought...if it ain't broke, don't fix it.
Chris
The lack of oil related failures in general and specifically in this forum speak for themselves. Modern engines are very forgiving.
OP
OP
Sidekick
Save Ukraine Stop War!
Measuring how much oil is expelled from the engine after a dyno run misses the real purpose of lubrication. It’s certainly not part of any lab-standard test. The real focus should be on how quickly oil pressure reaches the top of the engine during a cold start, when lubrication is most critical.
Beyond that, oil plays a key role in engine cooling and in carrying away impurities, which is why using the correct viscosity is essential.
Ultimately, what truly matters is the resilience of the lubrication film and the stability of oil flow under all operating conditions. That has little to do with what ends up in the catch pan after a full-throttle run.
Like everything else in the automotive world, engine oil is constantly evolving.
Maybe it's worth considering that progress has been made, and there could be better options today.
Beyond that, oil plays a key role in engine cooling and in carrying away impurities, which is why using the correct viscosity is essential.
Ultimately, what truly matters is the resilience of the lubrication film and the stability of oil flow under all operating conditions. That has little to do with what ends up in the catch pan after a full-throttle run.
Like everything else in the automotive world, engine oil is constantly evolving.
Maybe it's worth considering that progress has been made, and there could be better options today.
5w 40 has less film strength than 15w40. Both oils will flow the same above 20 degrees f. Now if you were riding all winter 5/40 would be better but if your intention is find a better lubricating film the 5/40 is not the way to go.