when im on small roads i use d3 coz i feel like the car accelerates faster.

and when im on the highway i use D4.

but the question is... if i use the trasmission on D3 will it ruin my transmission?(btw i only go up to 60mph on D3)

i got a 95 honda DX coupe with 197,000 miles

 

I think D3 is for more power for Uphill climbs..If you use it all the time like on the highway, then it'll just use up more gas..and you'll have MPG like a Ford F-250(....ok..more like a F-150). And using it won't messup the transmission...that's why it's there.

 

D3 keeps the transmission out of 4th gear (which would be overdrive on most 4-speed autos), D4 will let the transmission shift to overdrive.

The car doesn't accelerate faster with the gear selector in D3 than it does in D4, it just changes the top gear