How to Sync iphone contacts to gmail

All google syncing is done through the wireless connection now. Go to the Settings app, and choose Mail, Contacts, Calendars.

Choose Add Account... and select Gmail from the list. Follow the instructions to connect to your google account, and then select whether you want to sync more than your contacts.

Tested on my iPhone 3GS with iOS 6.1.3 (6.1.6 just updates a few security issues, no change to the contact/gmail sync)

Here is link to a wiki on how to do it: How to Import Contacts from Gmail to Your iPhone

Depending on what iOS you are running the steps may be a little different, but I don't think so. iOS 7 doesn't have the "mail, contacts, calendar" setting, but I don't think the 3GS can update that far anyways. I don't think that this will wipe out your iPhone contacts, but one problem I seem to have with it, is that it creates a lot of duplicate contacts if you have duplicates in both accounts. I fixed this by getting an app called Simpler. It cleans up duplicates and works much better for merging contacts than the stock contacts app, among many other features. It actually replaced my contacts app. It may not be compatible with your phone though.