Oil change:Hot or Cold

[Mark65]

Which do you prefer?
Would it not be better to change cold as the oil will be at its thinnest ie:10w and the oil will all be in the sump over night.
If its warmed up do the oil molecule additives not unwind and thicken up at its operating temperature ie:40.
Would do you think, im gonna try a cold one this time.

Mark
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07 Yamaha YBR125, 07 Honda CG125 , 15 CBR300R (Chocolate Crank, Deaded), 16 CB500FA, 19 Honda Forza 300, 70 Suzuki SV650

[Kickstart]

Hi

Oil gets thinner as it gets hotter, just that a 10W40 (for example) doesn't get as thin as temperature increases as a straigh 10 weight oil would.

Imagine a measure of how thick (viscous) an oil was. Say a 10W oil when cold is 100 when cold and 50 when hot. A 40W might be 200 when cold and 75 when hot (completely made up numbers). So a 10W40 would be 100 when cold (so thinner than 40W when cold) and 75 when hot (thicker than 10W when hot).

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[Mark65]

This is a crazy subject:
The viscosity rating of a multi-grade oil is broken down into two parts;

The number before the W is the "winter" or "cold start" rating. The lower the number the thinner the oil. This allows quick flow when the engine is started cold (cold crank). 90% of engine ware happens at this time due to the engine running in a dry state.

The second number is the viscosity rating of the oil at 100 C. The higher the number the thicker the oil giving protection of "metal on metal" ware when the engine is hot.
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07 Yamaha YBR125, 07 Honda CG125 , 15 CBR300R (Chocolate Crank, Deaded), 16 CB500FA, 19 Honda Forza 300, 70 Suzuki SV650

[MarJay]

Oil change fail.

I've done a LOT Of oil changes, and from experience the oil is always a LOT thinner when warm.

Do it when warm. Its what a Haynes manual would tell you, its what Keith tells you and its what I tell you.

Or do it when cold because you think you understand the heat range properties of oil. I don't mind as long as you don't come on here asking why your oil is dirty again immediately after an oil change.
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British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[Kickstart]

Hi

For a 10W40 oil it is saying that at the high temperature point the oil acts like a 40W oil and at the low temperature point it acts like a 10W oil. Sure at that high temperature a 40W oil will be thicker than a 10W oil, but it will be one hell of a lot thinner than a 10W oil at low temperature.

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[The Shaggy D.A.]

If I'm being real anal, I'll drain the bike after a run and leave it overnight.
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Chances are quite high you are not in my Monkeysphere, and I don't care about you. Don't take it personally.
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Previously : CB100N > CB250RS > XJ900F > GT550 > GPZ750R/1000RX > AJS M16 > R100RT > Bullet 500 > CB500 > LS650P > Bullet Electra X & YBR125 > Bullet 350 "Superstar" & YBR125 Custom > Royal Enfield Classic 500 Despatch Limited Edition (28 of 200) & CB Two-Fifty Nighthawk > ER5

[yen_powell]

Hot is best, then you get to play the 'where will it go' game. Into the catch tray or squirt past it and cover the floor?

This is followed by the game where you move the tray as the speed of the outpouring oil slowly drops and the distance it squirts decreases.

This game is easier if you are a bloke as urinating whilst standing up has similar properties.

Other games are also available with a hot oil change. Whipping away the piping hot drain plug without droppin it into the old oil is another goodn.
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[the grim reaper]

[Mark65]

Marjay chill, i have done with the engine hot, as per yamaha manual. I dont pretend to understand oil technology its seems to be a bit like women when you think you understand it it changes.

Thanks for the advice, bike is draining now.

Mark
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07 Yamaha YBR125, 07 Honda CG125 , 15 CBR300R (Chocolate Crank, Deaded), 16 CB500FA, 19 Honda Forza 300, 70 Suzuki SV650

[Timmeh]

For extra added hot oil game fun do it with the engine running and try to guess just how much oil you've got left before it runs dry! Winner is the one closest to get to the rebuild light (sorry oil pressure) coming on before you hit the killswitch.

(this of course is absolute bollocks)

I too, run the engine for 5-10 mins before draining.
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GSXR400 x2 | '94 RVF400 | '93 TZR125 4DL (again)
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[tshort2007]