Lucas Oil

Assuming you're using a multi-grade conventional engine oil now, then there shouldn't be a noticeable difference in the mechanical engine noise, which is almost entirely valvetrain. Improvement in shifting going to 75W90 Red Line gear oil, most assuredly - I noticed that immediately after changing from H-D SportTrans.

Hey, Hotrod it keeps getting better brother like Isaid I am sold on Red line."JAZZ" :roflmao:

And the Shockproof Light is blue - go figure

Actually the viscosity between conventional & synthetic of the same rating isn't the same - the rating primarily comes from the tests the oil can pass. Synthetic Red Line is actually straight-weight, but since it can pass tests like cold flow, it can (& does) carry a multi-grade rating & my understanding is that's basically true with all synthetics, although different brands use different basestocks.

A 20W conventional starts out being a 20 weight & then additives are mixed in to make it act like the 2nd number when it's hot (so says a chemical engineer I used to work for). While that works in a liquid-cooled, thermostatically-controlled engine that runs the same temp in January as in July, it does not work in an air (oil) cooled engine. What it boils down to is the conventional multi-grade thins out more as it heats up & has a lower viscosity index to start with.

I just pulled up the data sheets on 2 motorcycle oils for comparison - Valvoline conventional 20W50 & Red Line synthetic 20W50. The Valvoline has a Viscosity Index of 124, the Red Line 155. The Valvoline goes from 169.4 cSt viscosity @ 40 degrees C to 18.6 cSt @ 100 degrees C & the Red line goes from 148 cSt @ 40 degrees C to 19.8 cSt @ 100 degrees C.

We'll need a chemical engineer to tell us all about centistokes (cSt), viscosity index, etc., but we can see that there are some noticeable differences between the Valvoline conventional & the Red Line synthetic, including a higher viscocity index, a lower range from 40 degrees C to 100 degrees C & a higher cSt @ 100 degrees.