Iphone 4 fell in diesel

The general rule when a phone is dropped in liquid is to never try and turn it on until an Apple Store or an Apple authorized repair service can look at it. If you have an Apple Store in your area then I would book an appointment with the Genius bar and have them check it out. They will then advise you as to what your options are. If they are able to repair it the costs might be prohibitive given the age of the phone. You may be better off putting that money into a new phone but it doesn't hurt to get the repair estimate first and then make an informed decision.

I'm assuming you've not powered it on since this happened or are you actually using the phone? It's possible that it could be repaired by having someone open it up and clean it or it could require a whole new display. If you haven't yet powered the phone on then its likely there is more damage than what you can see and the phone could be damaged beyond repair.

There have been 9 newer iPhone models released since your iPhone 4. Given that this could be the perfect time to upgrade to a 6S or 6S Plus. The current iPhones have a larger screen and a massive increase in performance compared to the iPhone 4 and you'll be able to run the latest versions of iOS9.

Nobody here would know if it can be fixed. You would have to try and find out.

For water at least, buy a pound or two of rice and let the phone sit in the rice for a day or two in the uncooked rice.

http://www.copytrans.net/support/dropped-my-iphone-in-water-prevent-damage/.

R

Great! Have a good Christmas and a Happy New year too!

R