My bb stroked 427fe at 90mph, 3000rpm gets 17mpg. Done several trips to LA and LV. Surprised me - tho it does weigh like 2400lbs? Not a lot to push for a 460. Of course, the tr3550TKO with .68 OD 5th helps.

This kind of driving is probably the only time you'll ever use your TKO 5th gear.

I think 168 miles would be pushing it for me. Airpark did my installation (427 IR, Tremec TKX 5sp). When I originally picked the car up, Christian informed me that "the fuel gauge works pretty accurately from full tank down to half-a-tank, but after that the guage will drop to empty because "all Cobras do that."
From day one I use my trip odometer as my fuel guage. It ran out of gas on me once...as I was pulling into my driveway (Talk about luck!). The trip meter read 131 miles.

Currently, the car less then 800 miles on it. I'm averaging less than 9.0 MPG. Since it's new and shiny, the car only leaves the garage to attend car shows and back. Rinse and repeat. Some folks find that style of ownership annoying. I personally find newly discovered rock chips annoying.
Next year I'll start doing road trips - with a 50/50 I might pull a Tom Brady and stick with the car show routine for another season.

I'm convinced it's running too rich. Christian at Airpark says no. I called Bob Ream at Imagine Injection last week and he is in agreement that the car is in dire need of a proper re-tuning.
Hey - when you let off the gas and the exhaust starts popping so loud the traffic around you thinks it's a drive-by shooting, or your sitting at a red light and a guy in a giant truck next to you puts his window down and asks if the car has a fuel leak (it doesn't)...ya know it's running RICH!
But Christan at Airpark doesn't want to hear it. "It's running normal, sir".
Yeah, what ev's.

If all you are doing is short runs and getting on it frequently, you are not going to get great mileage. Drive it down the highway for 60 miles or so and check your mileage.

I appreciate the input MKS, but the poor gas mileage isn't a contributive factor, it's one of the resultant consequences derived from the principle issue.

This past Saturday, I met up with some fellow Cobra owners at a show in Vistancia. That was a 56 mile drive from the east side of town to the west side, via the 101.

Once I got off the highway and back onto surface streets, the motor acquired some surprisingly fresh, new, and annoyingly worse symptoms. At every light or stop sign the idle would go dangerously close to stalling, then recover after a few seconds. When starting out from a dead stop, the car would buck back-and-forth aggressively as if I was trying to pull out in 4th or 5th gear, and then recover itself whenever it damn well felt like it.

From my research, Imagine Injection in Glendale is overwhelmingly regarded as the best shop in Arizona when it comes to tuning fuel injected Roush motors. (Allegedly) The owner, Bob Ream, worked for Shelby for over 25 years.

I am waiting for an opening where he can slot my car in for a re-tune. I talked to him last week. Based on the engine symptoms I provided, he stated 2-3 hours of his magical touch @ $125/hr should put my 605HP EFI Roush back on it's feet. Stay tuned (pun intended).

As previously stated, I use the trip odometer as my gas guage, I fill the tank when it hits 100 miles. It always takes 13-point-something gallons to fill it. That equates to approx. 7.7 miles to the gallon.

The.Motor.Needs.Tuned.

Thanks for the info Bob!

My Roush 427IR got about 9 MPG in city, but 12-13 on highway in 5th at 75.

What generation of EFI do you have? If it is the Accel system (older generation) it's going to take a lot more than 2 hours since the tables are not completely populated and it will take time to discover the gaps. As discussed earlier, if that is what you have you would be well advised to switch to another system or go back to the carb version (427R). (under a grand vs 4grand). And a carb will do fine for your usage model.

It's a 2022. I took delivery 4 months ago in October. SPO3521

Tony - I wrote a check for a little over $50,000 less then 5 months ago to have a 427IR & TKX trans installed in that car. While I can appreciate you thinking outside the box, the notion of reverting to a carbureted engine has to be the most ludicrous suggestion of all suggestions in the entire suggestive world.

I know my ECU is a FAST. Bob seemed relieved when informed.

The suggestion was IF you had the antiquated Accel system. I made that pretty clear. Does not apply if you have FAST.

You should still be covered by warranty.

I meant no disrespect Tony. I didn't read your post carefully enough.

Roush builds a solid motor. I am of the opinion that when properly tuned by a properly qualified professional, my engine is going to sing nicely.....and my mpg will adjust accordingly.

As was mine when I finally got it tuned into submission. Many people complained about excess oil usage but I never had an issue.

I haven't seen one of the new units. Did they add a PCV valve or are both sides still using the K&N breather??? Many here say that they require a PCV valve but I've never been able to find a solution with the faux-Weber trumpets...

"My old carbureted 460 even gets 17+ on the road with a 373 rear"

Bob, We all know your 460 runs mainly on fairy dust. Quit making me feel bad! Please....

I've had three Cobras. None of them had an accurate gas gage. I used the odometer to calculate mileage for all three of them. I'm running a big block roller motor that gets about 12.5 around town and 13.5 on the highway if I drive slow. If I can push it up to fifth gear and 2300 RPM, I can get 18.5 MPG but I'm doing almost 110 MPH.. Ask Mesa Dave, Bob Broberg and I believe it was Bruce ... I wonder if the cop is still looking for the red car?

Capt. Nobody, Didn't Roush build a 510 CI motor a few years ago that were constantly breaking down and needing to be reworded and/or replaced? I believe therer were a coupld of them from our club members who wound up selling their cars because of it. I haven't heard a lot of complaints about the 427 shorts that they build, but I've heard a few.

Danr, the faulty Roush engines I heard about were 511s that the owners had to ship back to Roush, some more than once. I'm of the opinion that when a very premium price is paid, the product should be exemplary. My 2¢

You are correct Karlos. I missed it by that much!

A miss is as good as a mile.

I-40 East from Hwy 93 to Ash Fork is a disaster. Just back from a CA road trip and there are a zillion potholes, some of them seriously deep, on that stretch of the Hwy. I, along with the 18 wheelers had fun trying to dodge them all! Seriously, I counted 12 cars along the side of the Hwy with blown tires and I'm sure the low profile ones had wheel damage also. Just a heads up for the return drive from Kingman. I doubt AZ will have them fixed by then.