Honda specifying 10w30 in their bikes now...

[neil.]

Anyone got any opinions on this? Must have happened recently, but it seems Honda are speccing JUST 10w30 for use in their bikes (My CBF125 manuals says ONLY use that, and in a local Honda dealer Castrol 10w30 is all they have on the shelf!). I thought it was a bit weird, but spoke to a dealer and they said the lower friction was better and 10w30 doesn't sludge up as much as higher viscosity's. But won't 10w30 be more likely to thin out/break up at high revs?

[Bezzer]

It's nothing to do with revs the "weights" are to do with working and viscosity at different temperatures, looks like they are saying their engines don't run that hot nowadays. Using 10-40 was probably just an insurance and not really needed but with modern oils you'd expect them to work throughout their spec so I can't see why you couldn't use 10-40.
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I used to be indecisive but now I'm not quite so sure.

[stinkwheel]

They have done this for a long time now with quite a few of their models.

I'm 98% convinced it's just them being deliberately difficult and have been putting bog standard 10w-40 in both my and my fiancees hondas and am loosing no sleep over it.

I wouldn't worry too much anyway. The oil viscosity you should use varies according to the atmospheric temperatures. We should probably be changing to a different grade oil over the winter anyway.

If you buy a German bike, they have a chart in the manual showing which viscosity range to use for what temperatures.

As I say, I think Honda went for a "This will be fine in most situations and let's make it slightly obscure so they have to get it from a dealer." approach to oil selection.

This is the viscosity chart for oils for use in a Ducati Multistrada. As you can see, the difference between 10w-30 and 10w-40 is that the 10w-40 is suitable for use in very high temperatures. So Honda are probably correct in that there is no need for anything more than 10w-30 in the UK climate, but I can't see using 10w-40 doing any harm.
https://www.motorcycleinfo.co.uk/resources/6795/assets/images/Ducati_MTS1200/how_to_faq/service_maintenance/oil_change/multistrada_1200_recommended_engine_oil.jpg
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Kickstart]

Hi

Oil viscosity required will probably be down to the clearances the engine is built with. Thinner oil is better for power and fuel economy, as long as the engine can still cope with it. Any oil thins out with temperature, but as long as it stays within reason then that won't be an issue.

Probably also a fair chance that a typical 10W30 has a longer life than a 10W40 (wider viscosity range needs more additives, and it is these that break down rather than the actual oil).

All the best

Keith
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[von1papen]

Just as a question, but would it make any difference if you used old fashioned cheap mineral Oil in something like a CG?

With Oil changes being every 1000 miles I wondered was it worth putting the expensive stuff in.

[Kickstart]

Hi

Old style CG I don't think I would bother with anything other than a cheap mineral oil. Air cooled with wide clearances so probably going to contaminate the oil rapidly, and designed to be very simple and tolerant of lack of maintenance (unlike the older OHC Honda air cooled singles that would land up with the head and cams being one piece units).

All the best

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

[von1papen]

Thanks for the reply! It'll help keep costs down now