The reason i say its not electrical is its done it for a while with various starter motors and batteries, and recently ive fitted new bosch starter,twin batteries, split charge and a new alternator and all wiring either new or cleaned up and the problem is still there and also oil change made it worse so im thinking it must be somthing in the engine.
something like engine partially seized is my gut feeling, my engine overheated and cracked the cylinder head about 1 year ago so im wondering if this could be it. how do i check for seizing engine?
Now that you've mentioned the seizing idea i think the slow starting and oil light flickering all started about the time that it overheated