75 Mpg Rpm

Master baiter · Jan 26, 2015

What rpm are ppl running at 75 mpg in your automatic? Mine is at 2500. Wanting to do gears but not sure If I should go 3.73 or 4.10

vertigasen · Jan 26, 2015

I laughed for a minute when I thought you were asking "What RPM are you get 75 MPG at?" I am happy when I get 4-6 mpg in town!

What car is this for?

I used the APEX Garage Gear Ratio Speed Calculator, and here is what I got.

For the 4R70W, with stock gearing of 1st: 2.84 2nd: 1.55 3rd: 1.00 4th: 0.70, I used different gearings with stock tire size of 245/45-17s (25.7" diameter).

3.27 @ 2240 rpms = 75 mph
3.55 @ 2430 rpms = 75 mph
3.73 @ 2550 rpms = 75 mph
4.10 @ 2810 rpms = 75 mph

Master baiter · Jan 26, 2015

Lol yea stupid auto correct. He'll if that's so I wonder if mine has 3.73 already. Was supposed to b stock car when I bought it.

Master baiter · Jan 26, 2015

I don't want to kill my mpg. I bearly get 250 miles to a tank. It's horrible.

Master baiter · Jan 26, 2015

If it matters mine is a convertible

03_TrueBlue_GT · Jan 28, 2015

I find these cars get the best mileage at 65-70mph with stock gears. Granted mine is a stick and has 3.73 gears and the heavy deep dish rims I managed to get 24pmg at 65mph and that was really tough to do but I wanted to see what it could do. At 75+ I'll get like 19 maybe 20 mpg...

restomod66 · Jan 28, 2015

If you're spinning 2500 rpm @ 75 mph then it's pretty safe to say your car already has gears & that would somewhat explain your poor fuel mileage when compared to the factory 3.27 gear ratio.

Master baiter · Jan 28, 2015

Yea that's wat I'm wondering. I'll be pissed if I buy 4.10 and it has em. Lol guess this weekend I'll jack it up and find out.

vertigasen · Jan 28, 2015

250 miles on a tank is not crappy gas mileage! If you used every drop of gas in the tank (15.7 gallons), that would be almost 16 mpg. If you actually only have to fill up with about 13 gallons (when its on E, and not OUT of gas), then you would be getting almost 20 mpg. Those are combined numbers, not just highway or city. According to the EPA, I don't know what car you have, but a 2001 v6 COMBINED average should be 20 mpg, and a v8 would be 18 mpg.

I checked mine this morning, a small sample, but I typically don't go under a half tank. I put in $15.50 at $1.99 for 91 octane. That was 7.79 gallons. I went 91 miles on 7.79 gallons, for an average of 11.5 mpg. That is CRAPPY gas mileage!

Master baiter · Jan 28, 2015

I don't know we're every 1 is getting these gas mileage numbers from, especially the v6, but I got 440 To 460 to a tank in my 98 v6 5 spd. Averaged 29 to 30 mpg. My 05 auto gt got 27 to 28 and my 07 man gt got 30 to 31. Granted all my miles are hwy and average around 80 miles a day. So yes to me 18 mpg is horrible for a slow 2v mustang. My 93 5.0 average is 23 to 24 and runs 3100 rpm at 75. At which was the average speed of the others.

Master baiter · Jan 28, 2015

vertigasen · Jan 29, 2015

City: Represents urban driving, in which a vehicle is started with the engine cold and driven in stop-and-go rush hour traffic.

HERE is where all fuel economy information is located. What a car's GOVERNMENT REGISTERED MPG is for city, highway, and combined.

My driving is pretty much mixed, and I get 11 mpg. For what my car is, I will take it. I didn't build it to get great mileage, so I can't complain when my MPGs barely in the double digits. But just for reference sake, when I do drive from Colorado Springs to Denver, I typically drive ~85 @ ~2600 rpms and get 20+ MPG. My last trip to the VA, I got 23 MPG....

Master baiter · Jan 30, 2015

vertigasen said:
City: Represents urban driving, in which a vehicle is started with the engine cold and driven in stop-and-go rush hour traffic.

HERE is where all fuel economy information is located. What a car's GOVERNMENT REGISTERED MPG is for city, highway, and combined.

My driving is pretty much mixed, and I get 11 mpg. For what my car is, I will take it. I didn't build it to get great mileage, so I can't complain when my MPGs barely in the double digits. But just for reference sake, when I do drive from Colorado Springs to Denver, I typically drive ~85 @ ~2600 rpms and get 20+ MPG. My last trip to the VA, I got 23 MPG....

What gears do u have? Auto or stick? My main concern is 2500 rpm at 75 in my 02 auto convertible seems high. I want gears but I wonder if it already has them.

vertigasen · Jan 30, 2015

I have 3.73s (might be moving to 4.10s soon) with a T-56 Magnum 6-speed with a .80 5th gear and .63 6th gear. 2500 rpms is nothing. I know a lot of auto guys running 4.30s and driving on the highway. Greater performance will decrease gas mileage, more gas mileage will decrease performance.

I filled up again this morning. 7.75 gallons for 114.2 miles(2 days to work and back). ~14.7mpg. I have thought about guying a little Honda or something like that to get GOOD gas mileage to work and back. The 3-5k I would pay for that car, and the maintenance on it would cost more than the gas if I just drove my Mustang. My F150 gets better mileage than the mustang, but not much. 16-17 mpg.

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