Is 5w40 oil too thin?

Discussion in 'The Perfect Line and Other Riding Myths' started by Keithert, Nov 10, 2013.

  1. Keithert

    Keithert Long timer

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    I recently switched to Rotella 15w40 dino oil in both my bikes. I've been happy with the way they shift with this oil. I'm tempted to try the synthetic oil but it is 5w40. I don't fully understand the lower number part of a multi viscosity oil. Is it a 40 weight oil that flows like a 5 weight? Would the low 5w part cause any issues or leaks? The bikes are my Vulcan 1500 and Yamaha XT225. I'd also use it in various ATVs.
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  2. scootrboi

    scootrboi Long timer

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    I rebuilt the engine of my old German scooter in 1986, installing new bearings, seals and gaskets. After a run in period I put Mobil 5W-30 which I used for 7 years and about 50,000 miles. It worked very well and caused no leaks. I now use 10W-40 with the same results, changing oil every 2000 miles. The engine has 65,000 miles on the rebuild and still goes strong. This is a 175cc OHV fan cooled single. I have a nearly identical machine that I bought with a few hundred miles on it in 1992 (it is a 1965) and have run 10W-40 in it for 25,000 miles. It needed new rings at 20,000 miles. Oil consumption is according to specs.

    http://www.flickr.com/photos/29821169@N06/10636064063/sizes/o/in/photostream/

    This is the motor I rebuilt. I have it out after 27 years and 65,000 miles because the drive chain in the swingarm needs to be replaced. It ran in an oil bath of Mobil 1. I think the thin synthetic has worked well because the motor is so tight. I used to run it pretty hard, and it wouldn't overheat. Now I am more careful because I think it will run until I don't ride any more.
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  3. txwanderer

    txwanderer Been here awhile

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    Goody an oil thread!! :rofl

    Yanking your chain. Sometimes synthetic oil can clean things up and cause marginal gasket seals to leak. This is usually on older machines with what would be leaks anyway but the gunk has stopped it, FWIW. Hence the wives tale that goes something like synthetics will cause leaks. If you have an older machine that has never had it, this could be something to watch for.

    5W-40 is going to flow like a 5 weight at 32degress (0 C), and 40 weight at 212 F. (100C) in general. Some have slightly different specs, but that is supposed to be "standard".

    Said all that to tell you this. It will never be at the minimum temp weight, unless you ride when pretty cool. It will flow like a 40 weight when at operating temp anyway. The wide weight range concerns some folks as shear comes into play. Molecules start out coiled in the lower temps, straighten in the warm temps and give it the different charactoristics in flow. Transmissions tend to clip the molecules (shear) and deminish the weight differential. Not a problem for the rotella, it seems.

    Been using diesel oil in bikes for a couple of decades and never had one fail me. The 15-40 has the same soot and detergent properties so leaking shouldn't be a concern, if it ever was, and the oil holds diesel engines together. They are a very hostile environment as well.

    Check it out and see if it makes strange things happen. Some oil assist clutch systems don't like it, some do. That is the real concern as far as I can tell. You won't hurt anything giving it a try.

    Experts in ,,,3,,,2,,,1,,,
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  4. beemerphile

    beemerphile Unreconstructed Southerner Supporter

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    The engineers who built the two motorcycles and know the materials and clearances and probably did a lot of testing tell you what weight and spec of oil to use. So your plan is to disregard their advice and ask a bunch of anonymous people with different motorcycles; no stake in your outcome; and likely no credentials or testing done on your particular machines what weight oil you should use.

    Hmmm. RTFM comes to mind.
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  5. tvpierce

    tvpierce Been here awhile

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    In a word, yes... you can use the synthetic. Do your own research, but I think you'll find it's considered one of the best motorcycle oils available -- at any price. I use it in all my vehicles moto or otherwise: C-10 Kawasaki Concours (sold), Honda CX 500, Honda Big Red 3 wheeler, Volvo 940 Turbo (300K miles and counting), Mercedes 190E (sold/currently has 300K miles and counting), Toyota Sienna.
    I can't currently use it in my '96 R1100RT (which is spec-ed for 20W-50) because my valve guide seals need replacing. So the 40 weight synthetic causes pretty significant consumption -- about a quart per 1000 miles. If I run 20W-50, that consumption is about 1/4 quart per 1000 miles. (Hope to get to those seals some time this winter.)

    If an engine is spec-ed for 40 weight oil, then it doesn't matter if it's a 5W-40 or a 15W-40. The second number -- the 40 -- is what's important.

    The first number -- 5W or 15W in this case -- is the "winter" viscosity rating. So the 5W-40 flows like a 5 weight oil when cold (great for cold starts), but flows like a 40W oil at 100° C.

    The Amsoil site has an excellent explanation of oil viscosity ratings in layman's terms:

    http://www.upmpg.com/tech_articles/motoroil_viscosity/
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  6. scootrboi

    scootrboi Long timer

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    Before I rebuilt the engine on my scooter, it was run on 40W nondetergent oil for 16,000 miles, sat for 6 years, then I switched to Mobil 1 5W-30 and drove it hard for 6000 miles and disintegrated a main bearing. So probably the clearances were all wrong for thin synthetic. But the same engine renewed is a different story, with no end in sight. The bearings in this engine are big for a 175cc- 6305's on the crankshaft, and they are probably overqualified now.
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  7. randyo

    randyo Long timer

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  8. ZEmann

    ZEmann want to be riding

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    I didn't know that existed
    according to the specs
    I can run that in my diesel instead of the t6 5-40 and I would if I lived anywhere colder since oil forced injectors hate cold thick oil

    of course if it was going in my truck it would be going in my xr also

    edit well 0-40 is a Canadian only oil s I won't be trying it and there was comments about it being no good for wet clutches
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  9. AustinJake

    AustinJake DR650 - Versys

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    I switched my Husky from Mobil1 15w50 to a 50/50 mixture of 15w50 and 0w40 and it starts easier when cold, I'll be switching my Versys from 10w40 to the 0w40 soon.
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  10. khager

    khager Long timer

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    Ahhh another oil thread! :lol3

    I use the Rotella 15W40, except for the winter I use the Rotella 5W-40.
    Why not use the 5W-40 year round you may ask? $$$, I am a tight-ass!:deal

    With the temps here I only need the 5W-40 a couple of months a year.

    Also the Rotella is JASO MA certified or something like that, although I have been using it years before it was "officially certified" and many thousands of miles, with no problems
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  11. Pecha72

    Pecha72 Long timer

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    well in that case I´d just use what the manufacturer of that engine recommends, simple as that. (No offence.)
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  12. Anonawesome

    Anonawesome Scenic Rider

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    So, you want the oil to be thicker in colder temps? Seems to me like you would want it to be the other way around. Not an oil expert, just looking to learn.
    #12
  13. C/1/509

    C/1/509 Now with more sarcasm

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    Too thin for what?
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  14. k-moe

    k-moe Long timer

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    Would you happen to know where I can find S.A.E. 30 weight Husky brand motor oil (non detergent)? I don't want to run my machine without using what the manual calls for.



    All oil questions should be forwarded here: http://www.bobistheoilguy.com
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  15. davek181

    davek181 Long timer

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    From the oil studies I have read, the major problems with motorcycles and oil is the transmission and clutch sharing the engine oil. The friction reducers in car oil can poison your clutch disks and cause slippage. (happened to me)

    The other factor of the transmission gears in the engine oil causes a shear factor that you don't see in engines alone. The oil will eventually get sheared to it's lower or base level viscosity. So if you start with 15w/40, you end up with 15w. That is the sole reason I have not gone to 5w/40 Rotella, or 0w/40 Mobil 1.
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  16. windmill

    windmill Long timer

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    Something to consider,

    the oil recommended in the manual is rarely the best choice from the engineering point of view.
    The oils recommended for identical vehicles are often different in various markets.

    Besides the engineering considerations, there are also environmental concerns, average climate, expected typical usage, whats available, quality of available oils, government regulations, consumer expectations, and manufacturers warranty obligations.

    Intelligent research will reveal there are legitimate options, the biggest problem is filtering out sales pitch from fact.
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  17. k-moe

    k-moe Long timer

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    Any JASO MA certified oil won't cause clutch slippage issues. The JASO MA motor oil rating was developed spcifically to address the needs of motorcycles. There are a growing mumber of synthetic oils that meet JASO MA specifications.

    http://www.oilspecifications.org/jaso.php

    http://www.jalos.or.jp/onfile/jaso_e.htm

    http://www.jalos.or.jp/onfile/pdf/4T_EV_LIST.pdf

    http://www.jalos.or.jp
    #17
  18. kyns

    kyns Long timer

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    I use WD 40 oil in my engines.

    JASO MA can suck on it.
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  19. khager

    khager Long timer

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    I use coconut oil for a sweet smelling exhaust! :freaky
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  20. Tuna Helper

    Tuna Helper Rawrr!

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    Rotella, so I am told, doesn't have those friction modifiers. I've been running Rotella in my old Hondas for years and haven't had clutch problems.


    I run Mobil 1 syn in my Buell and Harley.
    #20
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