Motor Oil

[Angelus359]

Remember, tiny improvements multiply, not add.

[99LeCouch]

Running synthetic is good for the environment since it can go 2-3 times as long on a change. For the transmission, it runs cooler. That extends the life of the transmission before rebuilding. And, it requires fewer fluid changes since it doesn't degrade as fast.

Running the thinnest oil your car can safely run is another way to get statistically better fuel economy. A 0w-XX oil helps with cold-start lubrication by getting pumped around faster than a 5w-xx or 10w-xx oil.

I have 5k miles on the synthetic 5w-30 (well, it's really 5w-20 since it's a very thin 30 weight) on my Buick. It won't be changed until the springtime, when it will have accumulated 10-12k miles.

[WisJim]

Many years ago I discovered that my pickup truck would barely start with regular oil, but turned over fast and start well with the same weight synthetic, in bitterly cold weather (which we really haven't had in the last 20 years). That was what helped me decide to use synthetics--and the oil pressure reached operating range much quicker with synthetic oil, too. I tried synthetic oil (Amzoil back then) based on the recommendation of a friend with a diesel VW rabbit whose car sat in an exposed parking lot all day, and still started well at the end of the day, partly due to the synthetic oil.