10/40 or 10/30 weight oil - GL1800Riders
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post #1 of 50 (permalink) Old 05-12-2011, 02:17 PM Thread Starter
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10/40 or 10/30 weight oil

The manual recommends 10/30 weight but my dealer recommeds 10/40. What weight do you guys use?
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post #2 of 50 (permalink) Old 05-12-2011, 02:31 PM
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Let's see... I'm going to ignore the manual, created by the manufacturer of the product, and do what some dude at the dealership says or some people I don't know on a message board. There's some sound logic. LOL!

10w30 Full synthetic. Every 8,000 miles (as the manual states) whether it's needed or not. If you're in an area where it's always hot weather you could get away with 10w40.

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post #3 of 50 (permalink) Old 05-12-2011, 02:52 PM
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The manual states both 10/30 and 10/40 depends on climate temp. so both are ok unless you live in extreme heat or extreme cold.
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post #4 of 50 (permalink) Old 05-12-2011, 03:17 PM
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Originally Posted by Droptine View Post
The manual recommends 10/30 weight but my dealer recommeds 10/40. What weight do you guys use?
We all live in different climates. I would re-read your Owners Manual to see what it recommends for your climate.
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post #5 of 50 (permalink) Old 05-12-2011, 03:31 PM
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When the GL1800 was first released in 2001, the service manual called for 10w-40 oil. At some point in subsequent years (I think it was 2006) Honda changed the recommendation in the owners and service manuals to 10w-30 oil. Though I'm not aware of any changes to the lubrication system or engine that caused that change. I'm not sure what factors were involved in Honda changing the recommendation either, but I have a couple good guesses.

In some respects, 10w-30 is a superior viscosity simply because it doesn't contain as much VI (Viscosity Index Improver polymer) additive in it, which means it has a higher oil content to begin with. Some 10w-40 oils can have as much as 30% VI additive by volume, which means you have less lubricating oil to begin with, and VI additive by itself has no lubricating properties. Auto manufactures stopped using 10w-40 oil many years ago because it simply breaks down too fast, and my best guess is that this is also why Honda has shifted away from it.

10w-40 should work fine in all year bikes, but you need to be aware that it breaks down faster due to the higher VI content in it, so you'll need to change it a bit sooner. If you can find the brand you like in a 10w-30 blend, that would probably be a better choice. The only problem I've found is that it's hard to find any motorcycle oils in a 10w-30 viscosity.

Synthetic oil doesn't need as much VI additive in it to begin with, so a 10w-40 in a synthetic is also a good choice, and will probably hold up as good or better as a conventional oil in a 10w-30.

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post #6 of 50 (permalink) Old 05-12-2011, 03:34 PM
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In this case, I speculate (an educated speculation) that Honda began including 10-30 as a suggested choice, perhaps the primay choice, NOT based upon any mechanical foundation, but rather to improve their standing for federal fleet fuel efficiency averages. Unless I were in a cool area during most of my ridning, I would choose not to consider the 10-30 for this machine. In a cooler area, 10-30 may save you a few pennies in fuel cost over the service life of the bike.


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post #7 of 50 (permalink) Old 05-12-2011, 03:34 PM
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all the above-

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post #8 of 50 (permalink) Old 05-12-2011, 03:35 PM
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5w40 T6
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post #9 of 50 (permalink) Old 05-12-2011, 03:42 PM
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Originally Posted by jerrieric View Post
5w40 T6
I would NOT reccomend using a 5w-anything oil in a motorcycle where the transmission is lubricated by the engine oil. 5w-40 is made from a base stock 5 weight oil, and it's simply too thin an oil to protect your transmission.

Furthermore, I fully expect to be punished severely for posting on an oil thread, and I'm certain I'll regret it before the end of the day. Oh well....

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post #10 of 50 (permalink) Old 05-12-2011, 03:49 PM
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Use whatever is on sale, a good rule of thumb.

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