The most common is manual transmission fluid (MTF), which lubricates the ... Read more: Every Major Brand's High Mileage Motor Oil Ranked, Worst To Best Though often confused, gear oil and ...

In our tests, we've found that in some cars a manual transmission can improve gas mileage by a significant 2 to 5 mpg, compared with an automatic, and can cut a car's price by $800 to $1,200.