Quote Originally Posted by WATAJK View Post
1. V-Power is more recommeded as Shell have a larger majority of the market.
2. If u want great fuel economy shifting at 3000-3500rpm is an idea.
3. Yes you correct, underflated tyres kill ur economy but also overinflated isn't that great either, i have a set PSI on mine 36PSI which is generally the best for driving on but your car manufactor generally recommends another PSI as it increases the comfort for your drive.

Hope this helps
4 psi higher then the tyre recommendation/manufactures specs will give you better econermy and a slightly stiffer ride.
manufactures prefer a slightly lower pressure as it adds for a smoother ride.

you will notice the difference in stiffness with 4-5psi more and you will get better economey and will perform better,
but if you put to much in 6psi+ you will damage your tyres and there is no point to do them that hard.