simple questions

[Kaka-x]

Hi everyone
i have a 98 ex sport 4.0 ohv with 138 k miles on it
i have been using fords synthetic blend 10w-30 but want to switch to another type oil.
My question is
Is synthetic oil a good idea @ my milage and will there be any damage to my engine switching to this ?
What are the benefits of synthetic oil vs conventional oil ?
Is fords filter good with synthetic oil ?
What brands are best btwn Castrol / Mobil and Quaker state - these are all @ my local autozone.
Responses are greatly appreciated - WHAT WEIGHT IS ADVISABLE ALSO
Thanks

 

[BrooklynBay]

You shouldn't have any problems switching to synthetic oil. Thinner oils circulate better, so they are better for increasing gas mileage. Older engines with minor seal leaks, or bad piston rings would work better with thicker oils which don't get past those seals as easily. Some people prefer to use thinner oil in the winter, and thicker oil in the summer. Most brands should be OK to use. Most people on this site prefer Amsoil or Mobile 1 when they use synthetic oil. Check # 40, 41, and 43 in my list of useful threads for more information.