Does the FWD fuse in Subaru outback make any difference to handling fuel economy?

Answer 1

Disengaging the AWD with the FWD fuse, in theory, will improve your fuel economy.

I have seen a few Subaru 4 cyl. AWD automatics in my shop. However, my shop specializes on German cars so my knowledge is limited. Thus, I have a told my customers to only use the fuse as directed by the Subaru. That is, only when using a spare tire or being towed by a wheel lift tow truck.

There is unclear information on whether driving in FWD long-term damages the car (a good question to ask your mechanic or dealer). The way I understand it, adding the fuse disengages the electronically controlled differential. A much more simplified way of seeing it is that you are figuratively "pressing the clutch pedal in" for just the rear wheels by adding the fuse. In this case, there would be negligible or no extra wear on the drivetrain than if you had it in AWD. And keep in mind, the extra mass of the disengaged AWD components would still be in motion so don't expect to get the same mileage as a factory built 2WD Legacy.

Always, do your own research. The more educated you seem to a mechanic the more likely they are to give you an indepth view rather than a simplified "just do this because you won't understand" sort of answer.

** I have worked for Subaru for the past 4 years. You can not disconnect completely the AWD, on a four cylinder automatic (outback, legacy, forester, impreza- its the same drivetrain) the power distribution will be 60% front 40% rear. When there is slippage the center differential will electronically lock up to 50/50. Taking this fuse out will only leave you with 60% front and the inability to lock it 50 50.

On four cylinder manual transmission the power split will already be 50/50 but will allow for slippage or else parking your car in a parking lot would damage the drivetrain, but the way the center differential is built lets some slippage but will lock up when there is too much. Instead of being electronically controlled its a viscous coupling center differential, when there is slippage it creates friction and this viscous material inside solidifies with heat and completely locks up. This differential reacts very quickly and is very very reliable.

If you want to be baffled by mechanical engineering advancements research subaru's torsen rear differential which is found on the Subaru STI. Its a marvel of engineering.