Fuel economy question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

tiggamonsta · 02-13-2009, 09:01 AM

I was wondering what kind of fuel economy I could expect from the inline 6 with the 3 speed manual, and with a 4 speed manual if anyone has some numbers. The engine would be stock.

davidh · 02-13-2009, 01:32 PM

I think originally they were supposed to get 15mpg in top form. many will complain they get 8 or 9mpg. I had a 67 250 3 on the tree that got better mpgs than 350-auto trans trucks of the like. I think it got around 15mpg. If you have 4:11 gears and a 292 it might be harder to obtain but you could pull a house down at idle speed.
I'd add HEI to if I were you.

they help mileage and easier start ups

Oregoon · 02-13-2009, 09:14 PM

My 292 with 411s (in a '66 Burb) averages 11 mpg, and that's with a leaky carb. Of course, I have 17.5 wheels with OG bias-plys holding 60 psi. Going to a '71 307 rear soon, radials, and eventually, small four-barrel, long-tube header, and an electric fan. No power steering plans...

A guy here in town runs a Vintage Chevy parts biz, and has a '54 Coupe with a 235, and a powerglide. With a four-barrel, headers, and an easy right foot, he claims 22 on the highway. No idea what rear end he's running, but I can believe those numbers. I had a 258 in a Jeep Cherokee that got 15, and never ran right.

That said, the best fuel saving device I've ever installed in the Burb is a '64 Schwinn. Great for short trips, stylish, dignified, keeps me looking sexy (all things relative) and if the truck craps out, I'm never left completely high-and-dry... Especially here in Oregon.

tiggamonsta · 02-13-2009, 09:42 PM

THX for the info. Driving it is still a ways out,

but I am still struggling with keeping the inline 6 or go with something else. I had an 07 2500HD diesel that was bumped to 500HP and got 19MPG average. It is about finding that balance between Power, Money, and Efficiency. I was really hoping Chevy would release the smaller diesel they where talking about putting in the 1500 and H2. I would love to see if it proves itself. I would love to run bio-diesel in my truck, but those diesels still pull a premium $$.

pittdawg · 02-14-2009, 11:48 AM

I have a 66' long bed with a stock 250 and a 4 speed manual. Its my everyday driver. I commute about 50 miles round trip. Im have been averaging 14 to 16 mpg.

02-13-2009, 09:01 AM	#1
tiggamonsta Registered User Join Date: Aug 2008 Location: Cedar Creek, TX Posts: 167	Fuel economy question I was wondering what kind of fuel economy I could expect from the inline 6 with the 3 speed manual, and with a 4 speed manual if anyone has some numbers. The engine would be stock.

02-13-2009, 01:32 PM	#2
davidh Senior Member Join Date: Feb 2004 Location: Ponca city now kingfisher Oklahoma Posts: 1,220	Re: Fuel economy question I think originally they were supposed to get 15mpg in top form. many will complain they get 8 or 9mpg. I had a 67 250 3 on the tree that got better mpgs than 350-auto trans trucks of the like. I think it got around 15mpg. If you have 4:11 gears and a 292 it might be harder to obtain but you could pull a house down at idle speed. I'd add HEI to if I were you. they help mileage and easier start ups __________________ Even the nicest dodge-chrysler is only 2years away from being parked outside of Section 8 housing.

02-13-2009, 09:14 PM	#3
Oregoon Roadside Rebuilder Join Date: Oct 2008 Location: Southeast Portland, OR Posts: 421	Re: Fuel economy question My 292 with 411s (in a '66 Burb) averages 11 mpg, and that's with a leaky carb. Of course, I have 17.5 wheels with OG bias-plys holding 60 psi. Going to a '71 307 rear soon, radials, and eventually, small four-barrel, long-tube header, and an electric fan. No power steering plans... A guy here in town runs a Vintage Chevy parts biz, and has a '54 Coupe with a 235, and a powerglide. With a four-barrel, headers, and an easy right foot, he claims 22 on the highway. No idea what rear end he's running, but I can believe those numbers. I had a 258 in a Jeep Cherokee that got 15, and never ran right. That said, the best fuel saving device I've ever installed in the Burb is a '64 Schwinn. Great for short trips, stylish, dignified, keeps me looking sexy (all things relative) and if the truck craps out, I'm never left completely high-and-dry... Especially here in Oregon. Last edited by Oregoon; 02-13-2009 at 09:15 PM.

02-13-2009, 09:42 PM	#4
tiggamonsta Registered User Join Date: Aug 2008 Location: Cedar Creek, TX Posts: 167	Re: Fuel economy question THX for the info. Driving it is still a ways out, but I am still struggling with keeping the inline 6 or go with something else. I had an 07 2500HD diesel that was bumped to 500HP and got 19MPG average. It is about finding that balance between Power, Money, and Efficiency. I was really hoping Chevy would release the smaller diesel they where talking about putting in the 1500 and H2. I would love to see if it proves itself. I would love to run bio-diesel in my truck, but those diesels still pull a premium $$.

02-14-2009, 11:48 AM	#5
pittdawg Registered User Join Date: Jan 2009 Location: Kuna Idaho Posts: 31	Re: Fuel economy question I have a 66' long bed with a stock 250 and a 4 speed manual. Its my everyday driver. I commute about 50 miles round trip. Im have been averaging 14 to 16 mpg.



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