Originally posted by STORMINORMAN
I certainly agree with a couple of the latest postings. The concept that if 10W-30 oil is Good!, then 5W-50 is (somehow?) Better! and 0W-75 would have to be Best! has , I hope , already been de-bunked more than a few times...
I understand the downside to multivicosity oils is that modifiers displace the lubricant and have no lubricating properties. You can have up to 30% modifiers by volume in an oil. These modifiers do not lubricate. They are there to thicken the oil. The base mineral oil does the lubrication.
Another downside is that engine oils with a high amount of modifiers tend to leave more deposits than those with low amounts of modifiers.
It's for those two reasons I use 10W30 instead of 10W40 in my engines.
Therein lies the tradeoff.