Well last night I read a lot about this. Let me put in fine points here.
Fuel average difference will be minimal.
But all the off roaders advised to go for AISIN manual hublocks or LOKKA automatic hublocks.
And yes with permanently locked hubs there is bit of extra wear and tear in tyre and as well mechanical parts.
Now as you would be keeping this ride for a long time I would suggest as @engineermali already did. Change them to manual hub locks. AISIN hub locks from kabari I guess.
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