dear buntu bhai
1) mobil 1 fully synthetic engine oil 5w/50
its current price is rs4900 for 4 liter pack however i sourced in march 2012 at rs3700 
from army discount department store (csd )
other options are
a) caltux fully synthetic 5w/40
rs 2900
b) shell ultra hilix 5w/30
rs3500
( these rates were checked yesterday )
synthetic oils not only protect engine for longer time but also improve fuel avg and accelration
2) clay bar
this is professional product to clean the bonded surface contamination on car surface.
clay bars clean the paint surface even below the surface, some coaiminants grip, even penetrate the clear coat od paint like over spray, bugs, brids drops, tree spa, brake dust, road tar, oxcidation, industrial fallout, water marks, removes layers of older waxes etc
to remove all these things we have 2 choices
a) compound polish
compound is aggresive product which cleans these things but also eat up some layer of our paint clear coat so not very safe option.
b)clay bar
its safe for clear coat of paint surface and remove said stubborn contaminants , leaves your car skin feeling slick, smooth, cleaner look.
there are some precautions like first wash car with shampoo dry up and than apply clay bar pannel by pannel on cool surface by spraying detailer spray ( detailer spray contains waxes, oils and lot of water ), if you drop clay bar than its useless , dont give too much hand pressure etc etc 
its good for your 2007 gli and after claying you need to apply good wax
