GS-Riders International

For most engine applications, synthetic motor oils offer distinct advantages over non-synthetic or synthetic blends. Recently, here in the USA, all engine oils have had ZDDP (an additive employed for extreme friction circumstances) reduced due to the damage to the CAT caused by the phosphorus in the ZDDP. As a result, oils which retain their viscosity at elevated temperatures tend to provide more reliable protection.

Next, as mentioned, oil volitality (measured by the Noack test) at elevated temperatures can cause a non-synthetic to quickly go out of grade, reducing protection. Also, non-synthetic oils shear more quickly, further reducing protection.

Finally, synthetic oils tend to have high TBN (Total base number) which is the ability of the oil to protect against corrosion and resist formation of gum and varnish deposits.

Many boxer owners do not switch to synthetics at early miles due to rumors that the engine will not properly break in if synthetic is used. This is false. However, it is best to use non-synthetic engine oils during early miles because the engine will likely consume some oil in early life and the cost for synthetics is higher.

When should you switch to synthetic? The answer lies in your riding style, the climate you ride in and your oil change intervals.

If you ride hard, synthetics hold up better under severe conditions.
If you ride in cold or hot climates, synthetics offer better cold start flow and stand up to elevated temperatures.
If you change your oil less frequently than factory recommendations, synthetics offer protection during extended change intervals.

Here in the USA, Mobil1 15W-50 auto oil (not motorcycle specific oil) is popular. There are many boxer owners with in excess of 100,000 miles who use the Mobil1 without any engine malfunctions. It is reasonably priced and available about anywhere.