06-08-17, 03:38 PM
I stay away from any auto oil labelled Energy Conserving II as this will have friction modifiers that will screw a wet clutch.
I also avoid oils with viscosity ratings of 30 or lower; 0w30, 5w30 and so on. First, because Yamaha recommend a 10w40 oil for typical UK temperature ranges (-10c to 40c) and second because there's a possibility that these lower viscosity oils may have friction modifiers, even if they're not labelled as Energy Conserving II.
I discovered today that Yamaha used to list 0w30 oil as an option for use in extreme cold conditions but dropped that from later models. Rumour is that it was in part due to a number of clutch problems caused by owners using low viscosity auto oils which had unspecified friction modifiers.
Auto or bike-specific, everything I've read suggests that semi-synth oils tend to fall between two stools. They will be Group II mineral-based oils with perhaps 30% or so synthetic stock added. Since a mineral 10w40 will be pretty much reduced to a 10w25 within 1500 miles in a motorcycle motor, I don't believe - personal opinion, I stress - that a semi-synth blend will fare that much better. I like to go 4k miles between oil changes so that rules out semi-synth oils of any kind for me.
While it would be great to be able to use only one oil type in your Merc Sprinter and your bike, that depends on the viscosity rating Merc recommend for the van. If they're anything like FIAT specify for the turbo diesel in my motorhome, they might call for a 0w30 or 5w30 oil which falls under the 'too thin to be sure, don't use' criteria I follow for my Fazer and R1.
Since I live and ride in temps of 10c to 45c, my preference is a fully synthetic 15w40 or 20w50 C-rated (Commercial/Diesel) oil. The price point I aim to buy at usually means that the synthetic will be a Group III mineral-based synthetic rather than a PAO Group IV 'true' synthetic.
I also avoid oils with viscosity ratings of 30 or lower; 0w30, 5w30 and so on. First, because Yamaha recommend a 10w40 oil for typical UK temperature ranges (-10c to 40c) and second because there's a possibility that these lower viscosity oils may have friction modifiers, even if they're not labelled as Energy Conserving II.
I discovered today that Yamaha used to list 0w30 oil as an option for use in extreme cold conditions but dropped that from later models. Rumour is that it was in part due to a number of clutch problems caused by owners using low viscosity auto oils which had unspecified friction modifiers.
Auto or bike-specific, everything I've read suggests that semi-synth oils tend to fall between two stools. They will be Group II mineral-based oils with perhaps 30% or so synthetic stock added. Since a mineral 10w40 will be pretty much reduced to a 10w25 within 1500 miles in a motorcycle motor, I don't believe - personal opinion, I stress - that a semi-synth blend will fare that much better. I like to go 4k miles between oil changes so that rules out semi-synth oils of any kind for me.
While it would be great to be able to use only one oil type in your Merc Sprinter and your bike, that depends on the viscosity rating Merc recommend for the van. If they're anything like FIAT specify for the turbo diesel in my motorhome, they might call for a 0w30 or 5w30 oil which falls under the 'too thin to be sure, don't use' criteria I follow for my Fazer and R1.
Since I live and ride in temps of 10c to 45c, my preference is a fully synthetic 15w40 or 20w50 C-rated (Commercial/Diesel) oil. The price point I aim to buy at usually means that the synthetic will be a Group III mineral-based synthetic rather than a PAO Group IV 'true' synthetic.