Mileage expectations at 3000rpm
05-29-2018, 11:50 AM
#1
Burning Brakes
Thread Starter
Mileage expectations at 3000rpm
Hello all. I’m getting ready for a 250 mile trip in my 57 soon, and while I’ve always averaged about 13mpg in mixed-use driving, I’m wondering what to expect at sustained 65+ highway speeds. My car cruises at about 3000 rpm plus at 65, so does anyone have any recent experience under similar conditions? Been a long time since I ventured very far “from the barn”. Running a 350 low hp crate with dual wcfbs, M21 close ratio and 3:55 rear ended. And yes, I will make every effort to keep my right foot in check! 
05-29-2018, 12:51 PM
#2
Melting Slicks<br><img src="/forums/images/ranks/3k-4k.gif" border="0">
Member Since: Mar 2008
Location: Colorado Springs Colorado
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2023 C2 of the Year Finalist - Unmodified
Not sure what you might get, but my standard response to anyone asking what kind of mileage I get in my '66 L79, which has a Tremec 5 speed and 3.70 gears, is "I don't care!"
05-29-2018, 01:02 PM
#3
Race Director
Hello all. I’m getting ready for a 250 mile trip in my 57 soon, and while I’ve always averaged about 13mpg in mixed-use driving, I’m wondering what to expect at sustained 65+ highway speeds. My car cruises at about 3000 rpm plus at 65, so does anyone have any recent experience under similar conditions? Been a long time since I ventured very far “from the barn”. Running a 350 low hp crate with dual wcfbs, M21 close ratio and 3:55 rear ended. And yes, I will make every effort to keep my right foot in check!
I wouldn't count on anything more than 15 mpg if I were you. On my 67 with a ZZ4, Holley 4bbl, 3.36 axle and Tremec 5 spd I can get 21/22 at 70 mph cruise (that's 2000 rpm or so) - IF I behave myself.................
05-29-2018, 01:18 PM
#4
Burning Brakes
Thread Starter
Not on Maui now - in the Midwest with grandkids for an extended time. I remember getting about 18 in my 65 years back, but that was with highway gears probably about 2200 rpm or so. I know if I slowed my roll to 55 mph I would do better, but I’d probably get run over! Someday I may look into a 5 speed for this very reason.
05-29-2018, 01:19 PM
#5
Drifting
Member Since: Aug 2005
Location: New Baltimore Michigan
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I would guess less than 13mpg if you are at a sustained 3000 rpm, because you normally would not stay at 3000 rpm. Your cruising.arpund rpm is probably much lower. Let us know tho & enjoy yourself!!
05-29-2018, 01:22 PM
#6
Melting Slicks
I"d guess my car would produce MPG similar to yours. I also see about 3,000 RPM at 65 MPH. As I live about 25 miles by open road from my usual haunts, I'd guess about 80% of my miles are steady cruising at 65. I average about 14 MPG.
05-29-2018, 01:39 PM
#7
Burning Brakes
Thread Starter
Thanks for all the input. My fuel gauge is somewhat of a guessing game, as it stays close to full until I drive about 100 miles, then drops like a rock! 
As my dad always preached, I’ll keep it on the top half.
As my dad always preached, I’ll keep it on the top half.
05-29-2018, 01:48 PM
#8
Race Director
A lot depends on your motor, but if you get 13 mixed, steady state should get 15/16 on flat road at 65. Maybe 17 if everything in the motor is working together.
The cars are not super aerodynamic, going faster will get you a penalty.
Doug
The cars are not super aerodynamic, going faster will get you a penalty.
Doug
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capevettes (05-30-2018)
05-29-2018, 02:31 PM
#9
Le Mans Master
Hello all. I’m getting ready for a 250 mile trip in my 57 soon, and while I’ve always averaged about 13mpg in mixed-use driving, I’m wondering what to expect at sustained 65+ highway speeds. My car cruises at about 3000 rpm plus at 65, so does anyone have any recent experience under similar conditions? Been a long time since I ventured very far “from the barn”. Running a 350 low hp crate with dual wcfbs, M21 close ratio and 3:55 rear ended. And yes, I will make every effort to keep my right foot in check!
Jack
05-30-2018, 02:40 AM
#10
Pro
Hello all. I’m getting ready for a 250 mile trip in my 57 soon, and while I’ve always averaged about 13mpg in mixed-use driving, I’m wondering what to expect at sustained 65+ highway speeds. My car cruises at about 3000 rpm plus at 65, so does anyone have any recent experience under similar conditions? Been a long time since I ventured very far “from the barn”. Running a 350 low hp crate with dual wcfbs, M21 close ratio and 3:55 rear ended. And yes, I will make every effort to keep my right foot in check!
20mpg at fairly constant speed. (Thats Imperial mpg not US MPG !!)
from online converter abt 16.5
rebuilt L79, M20 wide ratio AutoGear Supercase with quick fuel Carb, CompCams Nostalgia Plus cam & trickflow heads
05-30-2018, 11:50 AM
#11
Race Director
Member Since: May 2000
Location: Redondo Beach USA
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Hello all. I’m getting ready for a 250 mile trip in my 57 soon, and while I’ve always averaged about 13mpg in mixed-use driving, I’m wondering what to expect at sustained 65+ highway speeds. My car cruises at about 3000 rpm plus at 65, so does anyone have any recent experience under similar conditions? Been a long time since I ventured very far “from the barn”. Running a 350 low hp crate with dual wcfbs, M21 close ratio and 3:55 rear ended. And yes, I will make every effort to keep my right foot in check!
Plan your return trip using the results.
Duke
05-30-2018, 11:59 AM
#12
Race Director
I think the OP was asking for opinions on what he might expect on the first half of the trip.........
