3 window

iTrader: (1)

So a week or so ago I had a buddy drive me around in the Nova while I tapped the keys on the laptop. On E85 with a 25-30 mph wind, we were able to get 16.5 mpg out of it at about 60 mph. Yesterday I threw a few gallons of pump 93 in it which gave me a blend of E45. Mileage went up to 20 mpg at 50 mph (and 19 at 40 mph). This is at 3400 lbs, a glide with a 17-0 converter, 3.55 gear and a 275 tire. I’m sure with straight pump 93 I could make it to about 24 mpg seeing it’d be about 14-15% less fuel than the E45 blend.
Note: I never touched the timing while tuning during cruise, only my target AFR. I’d bet there’s a mile or so in the timing as well.

Pro Stock John

iTrader: (34)

That's cool, what did it want? Get leaned out?

3 window

iTrader: (1)

Yeah, just leaned it out and watched fuel usage. Ended up 15-15.2 AFR above 45 mph or so.

LilJayV10

iTrader: (39)

I'm not sure why it's such a surprise that you get better mileage with less ethanol content.

3 window

iTrader: (1)

It’s not a surprise, just a statement about results.

Pro Stock John

iTrader: (34)

One of these days I'd like to check out your Nova.

jester1

iTrader: (1)

Ha no way! Get all you can get before you get greeted with this vision one day.

GMCGreg

That's $ 9.18 / gal. They're really killing us up here - mileage matters !!!

Ls7colorado

iTrader: (3)

So would advancing timing or retarding timing be better for economy? Ive heard both ways, seems in my mind advancing would help....

TrendSetter

leaner mixtures burn slower so you advance the timing.

Kawboom

I am pretty sure that this is simply untrue.

TrendSetter

so youre saying leaner burns faster in which case you retard the timing?

The BallSS

iTrader: (9)

gametech

iTrader: (1)

Being pretty sure does not make you correct in this case. The fastest fuel burn is typically achieved slightly richer than stoich. If you go leaner you definitely get a slower flame front. Lean burn also usually results in quite the annoying decrease in power, but the OP is looking at economy, so that is a whole different conversation.

Pro Stock John

iTrader: (34)

From what I've seen with single turbo LS builds, there is a range of timing they like for cruising and I'm sure Jamie (3 window) keeps it somewhere in there.

Jay Blanchard (a great wiring guy and fuel system and fabrication guy in Grand Haven MI) crews for a Nova like that that just won Summit Drag Week 8.50 index, they get about 10mpg on E85.