10W 40W or 10W 30W Motorcycle Engine Oil?
Discussion
I was in the Honda dealership yesterday and one of the items I needed to buy was engine oil. A couple of things had changed since my last visit.
The dealer was no longer selling Castrol GTX (I don’t know why), and they had two other options: the Honda branded motorcycle oil which was 10W 40W or the Morris Lubricants oil which was 10W 30W.
The man on the parts desk said that they use 10W 30W in the workshop. I have always used 10W 40W, so when I got home, I checked the user manual for both my Hondas (VFR 800F and CBR 300R) and sure enough the recommended engine oil is in fact 10W 30W.
I know that 10W 40W is considered better for use in warmer climates and while I don’t consider London to be a warm climate, most of my riding is through heavy traffic when the engine will be running at a high temperature, frequently with the fan on (for the VFR anyway).
Therefore, considering what the manual states, the climate I ride in, and the type of riding I do (mostly commuting in heavy traffic), am I better off sticking with the 10W 40W oil or will it not make much difference either way?
Maybe I should use the 10W 30W in the CBR 300R because its temp gauge never goes above the mid-way mark, even at the height of summer.
The dealer was no longer selling Castrol GTX (I don’t know why), and they had two other options: the Honda branded motorcycle oil which was 10W 40W or the Morris Lubricants oil which was 10W 30W.
The man on the parts desk said that they use 10W 30W in the workshop. I have always used 10W 40W, so when I got home, I checked the user manual for both my Hondas (VFR 800F and CBR 300R) and sure enough the recommended engine oil is in fact 10W 30W.
I know that 10W 40W is considered better for use in warmer climates and while I don’t consider London to be a warm climate, most of my riding is through heavy traffic when the engine will be running at a high temperature, frequently with the fan on (for the VFR anyway).
Therefore, considering what the manual states, the climate I ride in, and the type of riding I do (mostly commuting in heavy traffic), am I better off sticking with the 10W 40W oil or will it not make much difference either way?
Maybe I should use the 10W 30W in the CBR 300R because its temp gauge never goes above the mid-way mark, even at the height of summer.
Chicken_Satay said:
Maybe I should use the 10W 30W in the CBR 300R because its temp gauge never goes above the mid-way mark, even at the height of summer.
The water temperature gauge on anything remotely modern stays in the middle due to an in built damper so as not to panic the punter and also because the water is less prone to big movements due to thermostats and fans. If you had an oil temperature readout you would see that go up a lot in traffic and high ambient.
To the oil question I’d have bought the cheapest one as they will both do the job.
It's not a massive difference. The manual for my bike say 10W-30 and I use 10W-40 as it gets pretty hot here in the summer. Plus the Honda dealer said they exclusively put 10W-40 in absolutely everything, so I bought that.
Just make sure it's synthetic (GTX isn't) and you'll be good with either grade.
Just make sure it's synthetic (GTX isn't) and you'll be good with either grade.
Chicken_Satay said:
NS400R said:
Honda changed the requirement retrospectively to 10W30. Check with your dealer
When did this happen and why did they do it?Oh, a what oil thread ? 
If it gets hot most of the time, in traffic to use your example, I'd stay with a 40, if it runs cool most of the time, like commuting on a motorway, a 30 might be better, as per Honda recommendation.
Honda might have reviewed the upper viscosity in the light of the much improved viscosity stabilisers now used in oil, and the much more stable synthetic bases. They might have specified a 40 knowing that old oil tech would render it similar to a 30 when it got hot and used hard ? Maybe, just guessing.
If it gets hot most of the time, in traffic to use your example, I'd stay with a 40, if it runs cool most of the time, like commuting on a motorway, a 30 might be better, as per Honda recommendation.
Honda might have reviewed the upper viscosity in the light of the much improved viscosity stabilisers now used in oil, and the much more stable synthetic bases. They might have specified a 40 knowing that old oil tech would render it similar to a 30 when it got hot and used hard ? Maybe, just guessing.
SteveKTMer said:
Oh, a what oil thread ?
If it gets hot most of the time, in traffic to use your example, I'd stay with a 40, if it runs cool most of the time, like commuting on a motorway, a 30 might be better, as per Honda recommendation.
Honda might have reviewed the upper viscosity in the light of the much improved viscosity stabilisers now used in oil, and the much more stable synthetic bases. They might have specified a 40 knowing that old oil tech would render it similar to a 30 when it got hot and used hard ? Maybe, just guessing.
LOL. Just buy both and mix together, then you'll have 10W-35, best of both worlds!If it gets hot most of the time, in traffic to use your example, I'd stay with a 40, if it runs cool most of the time, like commuting on a motorway, a 30 might be better, as per Honda recommendation.
Honda might have reviewed the upper viscosity in the light of the much improved viscosity stabilisers now used in oil, and the much more stable synthetic bases. They might have specified a 40 knowing that old oil tech would render it similar to a 30 when it got hot and used hard ? Maybe, just guessing.
A modern road bike will be fine with either 30 or 40
Generally most have reduced the thickness for mpg / emissions reasons
There is the odd specific engineering case where a particularly thin oil must be used
The bigger question is why on earth you'd buy it from a main dealer ?
I buy oil in 20/25 litre drums off ebay - it only ever goes up in price and doesn't go off
Generally most have reduced the thickness for mpg / emissions reasons
There is the odd specific engineering case where a particularly thin oil must be used
The bigger question is why on earth you'd buy it from a main dealer ?
I buy oil in 20/25 litre drums off ebay - it only ever goes up in price and doesn't go off
black-k1 said:
As a cautionary note, a number of K1300S bikes suffered clutch slip/failure that was tracked to not using the exact oil specified by BMW.
To what extent was the oil used out of spec?I know 10W 40W will be fine for my bikes, because that's what I've been using for the last ten years. I suspect the reason that 10W 30W is specced is for mpg/emissions reasons, as mentioned by another poster.
I think I'll stick with 10W 40W, for the reasons mentioned, i.e., riding in heavy traffic most of the time with the engine in the higher temperature range.
Most of the answers here, so far, are fairly vague, meaning that the difference probably doesn't matter too much/isn't important enough to worry about.
Chicken_Satay said:
black-k1 said:
As a cautionary note, a number of K1300S bikes suffered clutch slip/failure that was tracked to not using the exact oil specified by BMW.
To what extent was the oil used out of spec?I know 10W 40W will be fine for my bikes, because that's what I've been using for the last ten years. I suspect the reason that 10W 30W is specced is for mpg/emissions reasons, as mentioned by another poster.
I think I'll stick with 10W 40W, for the reasons mentioned, i.e., riding in heavy traffic most of the time with the engine in the higher temperature range.
Most of the answers here, so far, are fairly vague, meaning that the difference probably doesn't matter too much/isn't important enough to worry about.
Chicken_Satay said:
black-k1 said:
As a cautionary note, a number of K1300S bikes suffered clutch slip/failure that was tracked to not using the exact oil specified by BMW.
To what extent was the oil used out of spec?I know 10W 40W will be fine for my bikes, because that's what I've been using for the last ten years. I suspect the reason that 10W 30W is specced is for mpg/emissions reasons, as mentioned by another poster.
I think I'll stick with 10W 40W, for the reasons mentioned, i.e., riding in heavy traffic most of the time with the engine in the higher temperature range.
Most of the answers here, so far, are fairly vague, meaning that the difference probably doesn't matter too much/isn't important enough to worry about.
Bob_Defly said:
The answers here aren't vague, we are all saying it doesn't really matter, because it doesn't. (10 years in the oil industry)
Great to have a gentleman of your experience onboard. Can you use your ten years' experience to provide details to help us understand the following comments from earlier in the thread? Please include links to the reference materials:"Honda changed the requirement retrospectively to 10W30. Original spec for the RR6 was 10/40." Why was it changed?
"Honda might have reviewed the upper viscosity in the light of the much improved viscosity stabilisers now used in oil, and the much more stable synthetic bases. They might have specified a 40 knowing that old oil tech would render it similar to a 30 when it got hot and used hard ? Maybe, just guessing." Is this correct?
"I'm certain I read that the instances of crank bearing failure on the VFR1200F was attributed to the wrong viscosity." Is this true or not?
"Generally most have reduced the thickness for mpg / emissions reasons." What details can you provide to help us understand this point better?
"As a cautionary note, a number of K1300S bikes suffered clutch slip/failure that was tracked to not using the exact oil specified by BMW." Is this true or not?
To give you an idea of how things have changed, the page below is from a 2003 VFR manual. A table like this also features in the manual for my old 1995 CB Two Fifty. The CBR 300R and most recent VFR manuals don't include this table. They simply state a recommended oil of 10W 30W. I don't know why this changed and I'd like to find out the details behind it.
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