Highway Gas Mileage

[Mcgiiver]

'95 Prizm, 1.6l, 3 speed auto, only 42,000 miles, well maintained. I am trying to figure out the best speed to drive on the highway to optimize fuel economy . I have been driving about 52 mph because that is the speed just slightly above where the trans convertor locks up. However, at that speed , I back up a lot of traffic. Does anyone have knowledge if driving at 55-60 would yield better fuel economy? Incidently, I am in no hurry to get anywhere.

[Frank Lee]

It's almost certain that 52 mph will yield slightly better fe than 55+. However if you are going 52 in zones where passing is allowed, don't worry about what's going on behind you. They can get used to it or pass.

[Sven7]

I usually P&EOC from 50-65mph. Best ecomod I've ever made:

[GRU]

haha that's awesome Sven7.

if you're like me and don't wanna hold up other cars, drive the speed limit. i can live with 60mpg vs. 65 (i'm guessing) for the 10 minutes of highway driving i do in a day.

[Soichiro]

There's certainly a difference. I usually drive the speed limit so as to not hold up other cars (although since nobody here follows the speed limit, I still find myself getting passed quite often), and I get about 4-5 mpg worse gas mileage on I-69, where the speed limit is 70, compared to I-465, where the limit is 55. Of course, the difference between 52 and 55 will be much less drastic, but there should still be a slight difference, assuming both are running at the same gear (as you said they are).

[Frank Lee]

The reason you can't put too much weight on cars behind you is, you can be going 90 in a 70 and there will be those who see you up there and feel they need to go 100 to "get in front".

[mcrews]

One thing I noted on my cross-country drives.....
Big rigs tend to drive 55mph.
I try to be conciderate of them since they are REALLY trying to get somewhere and are on the road for many hours. I would never 'force' a big rig to pass me because I was doing 52mph.

[HilseeJ]

To add on to Sven7's post, you can have custom bumper stickers made that say whatever you want. I personally chose:

PLEASE PASS
I'M HYPERMILING

Although I don't know if this will help when you're on the highway. But I'm assuming you might have the same problem in a city.

Originally Posted by Frank Lee

The reason you can't put too much weight on cars behind you is, you can be going 90 in a 70 and there will be those who see you up there and feel they need to go 100 to "get in front".

Quoted for truth. This phenomenon has baffled me ever since I was a child looking out the window on the interstate.

[slowbro]

Originally Posted by mcrews

One thing I noted on my cross-country drives.....
Big rigs tend to drive 55mph.
I try to be conciderate of them since they are REALLY trying to get somewhere and are on the road for many hours. I would never 'force' a big rig to pass me because I was doing 52mph.

I feel the same way. However I was recently driving on the interstate, something I rarely do, and I was driving 55 mph (the speed limit) and all of the trucks were still passing me. It was four lanes each way so when I noticed a truck coming up behind me, I would get in the lane next to the far right lane. That way the trucker didn't have to change lanes to pass, and as soon as he passed I would get back in the far right lane to let the angry people behind me pass (even though they could have passed on my left).

[JethroBodine]

Mcgiiver- The best way to get a definitive answer is to test it yourself. Someone with your exact same car could get a different result due to driving style, fuel pedal control, terrain, wind direction,... whatever. Discussing BSFC charts, aero modifications, weight saving, et al, will only get you started. Get an instant fuel meter of some kind, MPGuino, Ultra Guage,
ScanGuage,... and keep track of your daily numbers. Our member deathtrain fills up weekly at the same pump and logs in his fills in the garage here. Could be a good way to check the results of weekly 52 vs. 55 vs. 57 mph runs.

Have fun and let us know what you find.