In my opinion, he lies automatically, without any regard to anything. He lies when he has absolutely no reason to, as much as he does when he thinks he does have reason to lie.
The Washington Post does a lot of work on fact checking the president, and at some point they started counting his lies and misleading statements, probably when they realized that the volume of them was unprecedented.
Anyway - here's an update from the WaPo on the fact-checking.
It took president Trump 601 days to top 5,000 false and misleading claim in The Fact Checker's database, an average of eight claims a day.
But on April 26, must 226 days later, the president crossed the 10,000 mark - an average of nearly 23 claims a day in this seven-month period, which included the many rallies he held before the midterm elections, the partial government shutdown over his promised border wall and the release of the special counsel's report on Russian interference in the presidential election.Pretty impressive numbers - even more impressive than the reduction in the unemployment rate, the boost in the economy, or even the increase in military spending, for Pete's sake! These are historic numbers! The best ever! See how easy it is to be just like him?
The article notes that reaching the 10,000 milestone seemed "unlikely" back in the beginning when Trump was only making less than five false claims or lies a day - which means in a full four year term, he'd only end up with around 7,000. But here we are - and,
...the tsunami of untruths just keeps looming larger and larger.Let's see what that tsunami looks like.