Double-check your math: it's $4 per gallon, not $4 per mile.
If you're putting 5,000 gallons through each of six cylinders at $4 per gallon, that works out to $120,000 of gas. Certainly outweighs the cost of the engine by a decent factor.
If you're putting 5,000 gallons through each of six cylinders at $4 per gallon, that works out to $120,000 of gas. Certainly outweighs the cost of the engine by a decent factor.