I’ll be happy to get you on the roof so we can test it out

 

Might be more than you think. I've seen a test that suggested that running a loaded bike rack cuts your fuel economy by about a third on the highway. Even an empty back rack costs about 20%.

 

No way it is that high. Certainly it should reduce mpg though. I had my bike on the 911 for a 1200 mile trip and I averaged over 29 mpg surprisingly.

 

The width of a bike has a very small cross section all by itself without a radar so again, very little resistance, just as subshooter has proven.

 

I have 1-up rack on my Porsche. Best roof rack on the market. Low profile. Holds bike by tires only.

I had had to put a couple rubber dots to get rid of vibration when no bike is on the rack.

 

Nice!

how fast have you driven comfortably with bike on?

 

Highway speeds 75 to 80. But it’s rock solid. I feel like I could go any speed

 

and it looks like it holds two bikes? super cool setup

 

Id say easily could do 135

 

Actually I bought 2. You can buy just one.

 

Without knowing how fast subshooter was driving and comparing that with the mileage of the car driven at the same speed without the rack, we don't really know much. A bike has low frontal area, but a high drag coefficient because it has lots of components the air must flow around. Flowing around six 1-inch tubes in a row is probably as draggy as six 1-inch tubes side-by-side.

Here are some wind tunnel results for a Buick TourX that were measured recently:

 

Does anybody keep their rack on at all times? I don't mind how it looks and it's easier for me to just keep it on but am concerned about water and the gaskets/seals.

 

One of the main reasons I like my Seasucker - you can have it on and off in a minute or two and it stows easily in the frunk. I have the mini-bomber that holds 2 bikes - has 4 vacuum cups that each are pull-rated for 210lbs. (plus you have a 5th and 6th cup for the rear wheel support). I'm not worried about the bike holding. Additionally, if you have a sunroof, you can easily see the priming piston and recognize when you need to give them a few pumps (if you've had it on the roof for a while). It's a great system and I can fit a 700c road or cyclocross wheel in the frunk when the bike is on the car - and have plenty of room in the backseat for a wheelbag for an extra pair.

 

I drove from Wilmington DE to New Orleans over three days on interstates. Speed was about 70 mph on the highway and got 29MPG average. Up to 85 mph in some sections. I don't see me getting much better mpg. Certainly not a major reduction in efficiency. Of course it is a aerodynamic road bike though.

 

That seems like a reasonable estimate based on my experience. Bikes suck all aerodynamics out of your car.