Help me choose a viscosity?

[daz]

I have a triumph 1700 cruiser. It's a low RPM (6.5k redline) engine with a ton of low end torque as opposed to HP. It is a parallel twin, not a V and it's water cooled. I live in the L.A. area of so cal, so i ride in temps between 60 and 100 degrees. Mostly in 75-90 degree temps.

triumph recommends either 20/50 or 10/40. I've always used 20/50, but recently it occurred to me that a lighter oil like 10/40 would give me better power and better MPG, even if only a bit. But the question is, will there be any trade-offs in my case? Worse reliability or engine life or anything else? Or is 20/50 a better way to go in hot temps?

 

[Quattro Pete]

From a power/mpg perspective, I'm guessing the difference will be small enough for you not to notice it. I'd say give 10w-40 or 15w-40 a try and see how you like it. Some engines tend to sound a bit more noisy with lower viscosity grade, although it probably won't affect engine life in the grand scheme of things. If it doesn't sound right, you can always go back to 20w-50.

Also ask on some dedicated triumph boards to see what those guys are running in this engine and which grade they like better.

 

[daz]

well, those guys just go by what they *think* is best without any real knowledge, and if 10 guys answer i'll get 10 different opinions. I figured here being a oil forum i would find answers more based in fact.

 

[VR1]

Run what it calls for. You can't go wrong.

 

[Loobed]

Shell Rotella T6 Synthetic 5W-40. You will love it. I got about 3+ mpg improvement on my Kawasaki 750 4 cylinder aircooled bike. I took the engine apart after 90,000+ miles (I got hit), and it looked brand spankin new inside. The only part that looked bad was the piston tops and piston ring grooves.

 

[cmf]

Originally Posted By: daz
well, those guys just go by what they *think* is best without any real knowledge, and if 10 guys answer i'll get 10 different opinions. I figured here being a oil forum i would find answers more based in fact.


This forum is mostly opinion.

If you have access to peer reviewed tribology journals that is definitely your best option. There was recently an article on diesel fuel economy with different grades of oil. The ultimate conclusion from it is:

"A relationship between HTHS viscosity and SFC was found; increasing lubricant HTHS viscosity increased the specific fuel consumption linearly."

In a way that answers your question because more HTHS = more fuel consumption = more power loss (in a rough sense). The 40 grade should have less HTHS than the 50 grade but that's not how it is with every oil (some Red Line oils have much higher HTHS than the average oil of the same grade). This advice has been given by the more knowledgeable members of BITOG as well, so sometimes you get good advice that is scientifically proven.

The article can be purchased at: http://www.sciencedirect.com/science/article/pii/S0301679X10001854

I'm sure more specific articles exist, but I cannot think of them off the top of my head.

 

[cmf]

Sorry I mean it confirms not answers.

As far as engine wear with lower viscosity, I have not seen anything on that. I saw a test on piston rings where they felt the ring life was roughly 94k miles before they were not up to standards in performance due to increased blow-by. The test was done on a DOHC 1.5L engine. There are very few tests done on motorcycles because it's private consumers that purchase motorcycles.

As far as any test I've seen it really comes to the fact that it's miles put on an engine that wears it. Not using a certain viscosity, or not clean enough, or cold starts, or whatever other things most people seem to feel greatly affects engine life. Those are minor players in the game of engine life. But the fact remains that an engine will perform at a sub-optimal level for a long time after it's worn.

 

[Honda_Fan]

Originally Posted By: Loobed

Shell Rotella T6 Synthetic 5W-40.


All the protection that bike will ever need. The Rotella T 15w40 in your location & weather would be just fine as well, and almost half the price of T6.

 

[BigCahuna]

Most bike mfgrs give oil recommendations in the owners manual. It usually says to use a heavier weight oil in hot temperatures and a lighter weight if used in winter, when the temps are below 40 d f. What does yours say to use?.,,

 

[dwendt44]

IIRC, this is a water cooled bike. So heavy oil isn't needed even during August.

Rotella will work fine, either flavor.
Like some bike makers, they spec an odd weight oil so you'll be inclined to buy oil from them as those odd weights are hard to find retail outside the dealers.

 

[Robenstein]

Well I am guessing this is the new Thunderbird motor. If your manual is like mine *new speedmaster* it calls for a semi synthetic or full synthetic with a API rating of at least SH and for it to be JASO MA approved. So your best bet would be the Rotella T6 if you are concerned of keeping close to the manual for the warranty.

Personally id run the heavier oil. Like someone stated, your fuel economy should not suffer much running a 50wt over a 40wt.

 

[daz]

The manual specs either 15-50 (i just use 20-50, easier to find) or 1-40, but it doesn't say anything about which to use or why. I already know what oil i'll be using as far as brand....full synth Motul, 7100 If I recall. But i was just debating over whether it would be worth it to use lighter oil for the MPG and power. I've felt power increases before using synth over dyno that weren't at all subtle. So i figured lighter would also help power and MPG.

(yes, the new thunderbird)

 

[Robenstein]

You could try Mobil 1 10w40 moto oil and see how it responds. Im running Castrol RS Racing Power 10w50 in my new Speedmaster right now.

 

[RC46_Rider]

I put 25,000 miles on a Triumph Sprint 955. The owner's manual said EITHER 10W-40 or 15W-50 were "OK". I got curious enough to write Triumph engineering in England about the 10W-40 and received a reply saying it is FINE and "Commonly used". They had zero concerns.

I was not about to pay the rip off Dealer prices for the "special" Triumph Mobil 1. I used Mobil 1 10w-40 from Walmart and had zero problems and when the valve clearance was checked at 12K miles only ONE of the valves need a shim and it was "just barely" out of spec. All the foregoing is fact, not my "opinion".

I would bet you a TON of money that your bike will run "forever" with Rotella T 15W-40. Cold facts are that you probably will trade that bike LONG before you ever get even close to wearing it out. Unless you have aspirations of seeing 200K on that bike, "oil" is a "non-event" if you use a decent oil and change it at reasonable intervals. Rotella T, Delo 400 or Mobil Delvac all in 15W-40 all would seem to be an excellent and economical oil for your bike. If those oils will successfully stand up in Caterpillar diesel off road equipment running at full throttle for days at a time, KTM off road race bikes and many sport bikes, (which it DOES) it will be FINE in your Brit bike !!

If you really want to maximize "power", I would use the Mobil 1 motorcycle oil in 10W-40. (Or other premium synthetic 10W-40 bike oil) I and several friends have switched between it an various premium dino oils and you CAN tell a slight difference, especially in something like a GSX-R-1000 or other high rpm sport bike. You CAN feel a fractionally stronger pull, especially at high RPM. That is also not "opinion". That is based on oil "swaps" in Gixxer 1000's, RC-51's and a Honda VFR800. I confirmed that my Triumph triple also ran a couple of degrees cooler on the M-1.
Not enough to be significant, but the digital temp gauge did not lie.

Bottomline: there are a LOT of really excellent oils that will work very, very well in your bike. You just need to decide what is the deciding factor you want to optimize. One minor advantage to the 15W-40 dino oils is that they are significantly cheaper and you will feel a little less guilty about doing shorter oil change intervals.

 

[rraiderr]

How about running both oils and getting a UOA done to see which one held up better?

Lot's of the oils sheer down in bikes pretty quick so a 50 weight is not a 50 weight for long.

 

[mjoekingz28]

No facts here, but it just doesn't seem that you'll feel a slow revving bike be any quicker with a 40 vs 50wt. Like RC46 Rider said, in a 14,000rpm bike it will most likely build revs faster.

I'd settle for the 50wt. Or mix the 40 and 50 wt if you cannot settle on one or the other.

I do have a question about oil temps though. I had a water cooled sport bike and the only time the water temp creeped up was at a standstill. So obviously water temp is higher with less air over the radiator, but when is your oil temp at its highest on the street, idling or cruising?

 

[daz]

Originally Posted By: mjoekingz28

I do have a question about oil temps though. I had a water cooled sport bike and the only time the water temp creeped up was at a standstill. So obviously water temp is higher with less air over the radiator, but when is your oil temp at its highest on the street, idling or cruising?


Can't say. no temp gauge, just a overheat light.

 

[Robenstein]

Some company, cant remember which, makes a temp gauge for Triumphs that just replaces the oil filler cap.

 

[KW]

Either oil is probably fine to use. But with no cold starts to worry about I would run the 20W50 oil.