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Oil Viscosity

Discussion in 'Bling and Appearance' at netrider.net.au started by mr_messy, May 18, 2007.

  1. I was wondering what is the lowest possibly oil viscosity I could use for my little ninja, zxr250c.

    I've recently changed from a 20-50w rating, I think, to a 15-40w.
    It obviously feels better having fresh oil.
    I was thinking of maybe a 10 rating but was wondering if that was too thin.
    Reason being, compared to the older oil I was using, morning start and idle seems so much better. I don't have to have the choke on, reving it at around 4,000rpm at 4am in the morning.
    It still jumps up and down to 4,000 but after a few seconds I can take the choke off without it stalling.

    Anyway is there a thinner oil and is it safe to use on my bike?

  2. you can use a zero if you can find it. What is more important is the higher rating for temperatures in Oz. (The bottom number is more for people who live in areas where they actually need antifreeze). As long as it has a 40 or 50 at the top (or maybe 30 if you live in tasmania) it'll be fine. The thinner ones will generate more startup noise though, and cam chain tensioners that rely on oil pressure (yours isn't one) can take longer to settle.

    The wider the grades however, the faster the oil breaks down - you need longer and more complicated polymers to raise the base fluid to the highest viscosity rating than the narrower ones or ones with higher viscosity base stocks like the 20W50's, 10W40's etc.

    You can find 0W40 and 5W50 if you are sadistic and feel like wasting money!
  3. the larger number basically represents the recommended ambient maximum temp. so at this time of year you could probably run an #W-30 no problems.

    The lower figure indicates the lowest recommended temp but is a bit weird. i.e a 20W is recommended to -10 and a 10W is recommended to -20. 15 W is -15
  4. :-k :facepalm:
    so being winter I should/might as well get a thinner grade oil.
    Reason for the question is; I've heard of oils being too thing and leaking past the seals.
    Being an old bike with old seals I don't want it too leak.
  5. the question is not will it 'leak' but 'how much more'.
  6. 10w-40 is a nice number for winter in Australia.
    The lower the first number, the thinner the oil is at low tepmeratures, and therefore, the better it will flow when cold.
    The big advantage though, is teh thiner oil produces less drag on the moving parts, and also means teh oil pump doesn't have to work as hard when cold to pump that thick oil around. This is what you are noticing.
    I've had car engines that have noticeably dropped RPM's on cold start when oil pressure registered on teh gauge( oil pump loading up).
    If teh engine doesn't leak and oil pressure stays fine at temperature, thinner oil is usually better in winter.

    Regards, Andrew.
  7. I think full synth is thinner than blends or dino oil.
    10W40 is the recommended oil for my bike, just bought some today...
  8. My bikes recommended oil is 10-40, i thought id experiment a little and got some 10-50 last time i changed it. That was 3000kms ago and i had to top it up a little today, maybe 300ml. Hasnt been blowing smoke or leaking, i think my bike has it broken down over the kms??

    (sorry for the hijack)
  9. No, a 10w-40 is a 10w-40. It is oil viscosity that is measured for the classification.
    However, synthetic oils flow better when cold, and retain their viscosity when hot better that mineral oils.

    Regards, Andrew.