Friend guy's behaviour has changed - is he into me?

ok, so we are mates, and i've always thought he was cute, but as am a bit older thought he was never going to be interested.

me, guy and other guy friend in car mentioning him flirting with another girl mate, and he denies it quite strongly, almost defensively, and went quiet when I said, 'no I thought you were into her too."

we have a shared hobby and he helped me out and gave me lifts when my car was getting fixed, and genuinely didn't need to, and message back and forth re lifts- responses have previously only been thumbs up.

our interactions are always fun and exciting, like im never bored and neither is he, we genuinely have a good time with each other, and i put him into matesville in my head, so im really relaxed around him. there's been a bit of each of us teasing one another a bit, flirtyish - but again since he denied it re the other girl i was like ok he's just being friendly...

now he's going away and taking a long trip, that we'd discussed after a long car journey where we both were full on in convo about music and what we loved, singing along to random songs on my playlist etc and poor mate in back id almost forgotten about because we were bouncing off each other so much.

Missed saying bye before he left, text him and made a joke re what we'd previously said, hope you have a good Christmas and safe travels ' expecting our usual thumbs up.

but he replied with the heart emoji - age gap has me doubting - is it thanks / like / something else due to these other things

he was surprised i was older - approx 8 years - and commented you def don't look older, and appeared to be then thinking about it a lot.

Am i just confusing myself? do i see what happens when he comes back or message when away? i don't wanna mess anything up or miss a possible good thing - but if he's not into me I'm not so insecure that it would be an issue to me, more that it'll be a bit embarrassing!

thanks

Friend guy's behaviour has changed - is he into me?
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