I'd go by the temperature chart and weight oil recommended.
For most warm climates, 10W40 is fine for street.
It's not necessarily the weight of the oil, it's also the other ingredients/additives that enhance the quality of the oil.
Especially for bikes which use wet clutches and share oil with engine and gearbox.
Back in '04, a magazine had an issue where the tested several brands/weights of oil, both petroleum and synthetic.
One very interesting test was to try and de-bunk the myth of synthetic oil having less friction.
They took a stock Yamaha R1 and Suzuki GSXR1000 and dyno'd them with 10W40 petroleum oil. Then drained and filled with 10W40 synthetic, then re-ran.
To their surprise, both bikes showed an increase of HP across the entire rev range with peak HP increase of about 3.3 HP at 12500 RPM. Just from oil.
Now that wasn't 3.3 HP over the entire rev range of course, but there was a measurable difference from at least 2000 RPM.
Yeah it surprised me too.
I was just trying to find test results for various types/brands of oils to determine the best overall properties for use in my bike.
I had my suspicions since I had changed my truck oil from 10W40 petro-based to full synthetic and gained 2 MPG with highway miles.
To add to the already emotionally-charged subject (like discussing politics or religion--either stirs the hackles) I don't have much use for the "semi" class of lubricants. Either go full synth or stick with dino. Kinda like mid-grade gas. The worst of both worlds rather than the best, IMO.
Yeah I've wondered what properties the mineral based oil could add to the synthetic base.
Everything I've read about full synthetics showed improvements across the board compared to mineral based oils.
I've run semi-synthetic before, but decided to go full synthetic again as there was no price difference.
I agree. Price really wasn't an issue anyways.
What I was trying to understand was what benefits the mineral-based oil brought to enhance the synthetic oil.
So far I've seen none that synthetic doesn't already do better.
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