I'm thinking of purchasing a hood deflector for my 2011 Santa Fe, but I'm concerned about the potential decrease in gas mileage. Would adding a deflector do more harm than good in this case?
In most, if not all cases those mess up the aerodynamics. On one vehicle I once owned, it had one on when I bought it. I gained 2 MPG just by taking it off.
I had the same bad experience on a Ford F150 pickup. Lost 2 mpg with a aerodynamic hood deflector. Never again.
If you're interested in protecting the hood from chips they do make pre-cut clear protection film kits for your vehicle. The quality kits are not cheap $200 plus and over time it will yellow due to weather and the sun but cheaper than repainting the hood. Google, Paint Protection Film 2011 Santa Fe.
When I purchased my gen 2 Prius it had one installed by the previous owner. It gets excellent fe, and I like it on there. I'm happy, that's all that matters. H
I had one on my Suburban back in the day. I didn't keep meticulous mpg records but never noticed any effect one way or the other. Of course, it was a boxy 80's model so I'm not sure you could make it any worse.
Back circa 1980, there was a story that GM employees doing durability testing of new Chevy pickups accidentally discovered that certain bug deflectors improved aero drag and mpg. Of course those trucks likely had considerably higher drag in their naked state than today's.