What's seen as the optimal highway speed..?

[cheapybob]

Generally, its about 40 or 45 mph in my cars on flat pavement at a steady throttle, and resulting steady speed. I can get about 70 mpg if I do that, but the reality is that my time has some value, and so does my life, so I typically run about 60 to 65 in a 55 zone and stay in the slow lane to keep from being run over.

[DarbyWalters]

I just think the majority of people don't get it! They really don't realize how much 10 mph will affect mpg figures...they don't even check thier air pressures.

[GasSavers_Pete]

Originally Posted by baddog671

The autobahn with no speedlimit actually has a low accident rate..ironic...

More the fact in Germany a driver's licence is considered a privelege not an automatic right.
People take pride in driving there and although speeds on the autobahns are higher the quality of driving is first class.
Poor drivers are not well tolerated !

Pete.

[JanGeo]

Had to take a trip from Newport to Boston Logan airport and back yesterday and my friend drove us up in her Prius and got 52.9mpg for the trip there and I drove back alone and got about 62mpg going a little slower but also hit the Boston 93 south rush hour traffic for 40 minutes but I tell ya the electric battery got a good workout in that traffic - was going up hill on electric only for some time at 15-20mph and that saved a lot of gas. Tricky part was all the high speed slowdowns for no reason that lost some regen braking although I did manage to regen brake a lot. Watching the instant MPG on the dash when the ICE was running was very interesting on the up hills . . . man that car is heavy - I saw lower MPG reading than I would in my xB. Kept my speed at 60-65mph most of the time going a little higher a few times and 50-55 sometimes too.

Side note do any of you Prius owners find that car tends to wander a bit - I seem to have a hard time keeping it going straight and the steering seems very stiff with 18k on the odo.

[DarbyWalters]

This is where the Scan Guage will let a specific car show the best mpg/mph

[spacepilot]

For my car, the most fuel efficient speed is 45-50mph(72-80k/h). That's about the lowest speed where the transmission stays in the top gear on moderate hills. I can get about mid-40 mpg at that speed (EPA = 29mpg highway). At 60mph, the mpg drops to mid- to high-30's.

I agree with guest001 that turbocharged cars is a good both for performance and fuel economy. My car has a 2.0L turbo engine. When I really lay on it, the 3500lb car accelerates from 0-60 in about 7 seconds. But when I take it easy, I've got close to 40mpg on trips doing 60mph in sub-freezing temperatures.

[Rayme]

I'm sure I could get a better MPG rating if the awd wasn't permanently activated. All that extra differentials and shaft drag probably eats up some MPG, I can feel the car "braking" buy itself between shift when its real cold and the transmission/differential oils are still thick.

[rpm]

For steady-state driving, you'll want to be going at the slowest speed that your car can pull in top gear without lugging the engine.

[LxMike]

in my car the torque converter locksup at 42 mph. from that speed up to about 50 mph not much difference in mpg. maybe 1 mpg difference max. at 42 mph it's about 42 mpg and changes between there and 43 up to 50 mph. after 50 then aero and engine speed start to take over and it drops to about 37-38 at highway speeds of 65-70 i've even gotten to torque converter lockup and if i'm easy with the gas pedal i can keep it lockup while i drop speed to 37-38 mph but still not more than 43 mpg. A manual tranny might be different as to best speed for mileage.

[Hateful]

Same as above, I get best mileage at 43 mph( 52mph works almost as well in higher speed zones) and can maintain good mileage down to 37mph once I've gotten up to 43mph; before it gears down. Light footing the pedal makes a big difference in the trans staying in high gear. I alway keep an eye on the ScanGauge.