Bob, I have been using the 15W-50 full synthetic with good results [even winter as you said] and also knowing the bottom half of the engine is well protected gives me good peace of mind. Relating to an older thread about NGK spark plugs, the correct and best NGK plug to use is the BPR6 ES. This plug is what the engine build/design took into account - solid copper core. The 6 rating is medium heat range and I have used this plug on my Merak for many rears with excellent results. Once the carburetors are correctly sorted out, these plugs will amaze you. If the carbs are not correctly sorted out and the plugs are misread to indicate going to a hotter NGK plug [ # 5 rating] as conventional wisdom may suggest, damage to the engine could occur and the engine will not reach its needed optimal performance level. Just Sayin! Ciao, George
