LT1 Gas mileage MPG (Page 1/1)
str8maxn JUN 21, 11:32 AM
For the LT1 Swap owners...

What kind of a of gas mileage are you seeing?

Easy day to day driving and race to each light driving?

Thank you
JM
Dennis LaGrua JUN 22, 04:38 AM
As you may know, the LT1 is a high horsepower performance not an economy engine. Only a few Fiero owners have this swap but from what I can find online , the combined gas mileage of an LT1 in a Corvette runs from 16 to 21 mpg (data from actual users). I would figure 10% more in the lighter Fiero but gearing will have a huge effect.

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cyrus88 JUN 22, 03:05 PM
I get 14-18mpg, but I don't drive it gently enough to get better. Then again, I didn't swap in the Lt-1 for the iron Duke because I was interested in fuel economy.
fieroguru JUN 22, 04:52 PM
Depends on the transmission. The upper limit on the getrags is about 23 mpg at 75 mph due the pumping losses of pulling heavy vacuum at 2700+ rpm.
F40 should be able to get in the 28 mpg range due to the lower cruise rpm which also drops the vacuum at cruise.
4 speed auto should be able to get 26+ mpg depending on the gearing and cruise rpm.

For the V8s, cruise fuel economy is all about getting the rpms down and the throttle blades more open to lower the vacuum (pumping losses).
pmbrunelle JUN 22, 07:28 PM

quote
Originally posted by fieroguru:

Depends on the transmission. The upper limit on the getrags is about 23 mpg at 75 mph due the pumping losses of pulling heavy vacuum at 2700+ rpm.
F40 should be able to get in the 28 mpg range due to the lower cruise rpm which also drops the vacuum at cruise.
4 speed auto should be able to get 26+ mpg depending on the gearing and cruise rpm.

For the V8s, cruise fuel economy is all about getting the rpms down and the throttle blades more open to lower the vacuum (pumping losses).



Do you happen to have an example with typical numbers?

For instance, vacuum at 75 mph in 3rd, 4th, 5th, 6th with your LS4/F40?

Edit: I found this cute picture on Quora. Not a V8, but similar shapes I suppose?

[This message has been edited by pmbrunelle (edited 06-22-2022).]

str8maxn JUN 23, 11:52 AM
I estimate I'm getting around 12-14 MPG. Driving it like I stole it. So that appears to be within range.


Thank you all.
La fiera JUN 24, 10:29 PM
That LT1 I built into a 377ci just got bought by the original owner after 7 years! I went to get the car appraised to get bought back and as soon as I heard the motor start and Idle I said: Buy it back!!!!!! It sounded like the first day I built it. I'll get back to you on the gas mileage. it is a a 6 speed manual. It Dynoed at 431WHP(504BHP) and 497WTQ(582BTQ) Thats's 1.54 LBS per Cube!!. With a catalog cam and stroker kit and I did all the head porting. Gas milleage is not the norm here, performance is.

[This message has been edited by La fiera (edited 06-24-2022).]