I am using Loncin GP250, 250cc oil Cooled engine. After 500km run, I used motul 20/40 engine oil. Problem is, engine is heating too much. Question is what is the recommended engine oil grade for 250cc oil cooled engine. Thanks

  • How do you know it's too hot? Do you have an owners manual, and what does it say regarding oil weight?
    – raydowe
    Commented May 15, 2017 at 7:38
  • Nope. Even my fuel tank became hot.
    – ruddra
    Commented May 15, 2017 at 7:44
  • 1
    @ruda, that's​ not evidence of anything. on a warm day, when I leave any of my bikes out in the sun even the seat gets so hot I can't sit down and that's even without the engine running. you need evidence to judge it's running too hot, spark plug damage? and even then i monitored a very similar 229cc cg type to your 230cc cb type with an infra red thermometer and still didn't detect the valve burn as the temp on the head was in spec while obviously too hot in the chamber.
    – axa
    Commented May 17, 2017 at 23:27

1 Answer 1


I would try to figure out why it is overheating before getting a new oil. Though I don't see a Motul 20w-40 on their product page, I assume you are at least using motorcycle oil?

What kind of temp ranges are getting and what is the climate.

Oil choice in Alaska is going to be a lot different that Dubai.

  • thanks for the answer. I am not sure why its overheating. Current temperature in here is about 30 Degree Celcius. Maybe heavier oil should be better :)
    – ruddra
    Commented May 13, 2017 at 17:04

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