New guitar , old string , intonation...

[Aaabii]

Hi i recently bought a new guitar and i am experiencing tuning and intonation problems with it.
The strings on them are 10-46 as stock and they are really old. Besides from the look of the strings they already lost their acoustic sound, Guitar itself produce almost no unpluged sound as it is.
I'll try to explain my problems as best as i can but please excuse my bad English :

First of all ( you must be bored of hearing this but... ) guitar doesnt stay in tune. tried stretching the strings , retuning them after big bends but it didnt work. Interestingly strings go sharp moments after i tune them , ( i know it sounds weird ) i stretch the string , it goes flat , i tune it to the perfect pitch and a few minutes later
i observe that its sharp 5-10 cents

Second is its intonation. When i check , 12th fret is the same with open string. ( maybe +-1-2 cents) but on some frets its sharp like +4-5 cents.

My guestions are :

1-Can old strings cause these kind of problems or is it a faulty instrument ?

2-I play Drop D and i am really happy with the string tension of upper strings. Is using a 10-46 a mistake ? Can it harm the instrument ? If not can you please recommend me Ernie Ball set ?

Thanks for reading. Waiting for your answers...

 

[beej]

First off- yes, old strings will very likely give you intonation headaches. There's good reason to set your intonation on new strings.

As for the gauge, nothing wrong with 10-46. If you like the tension, get a new set!

 

[TNT]

Aabi, run out aand get a set of Super Slinky 9-42. Put them on the guitar and then double check every step of a "set-up"!!

Now, isn't that btter?!