Gas Milage - The 1947 - Present Chevrolet & GMC Truck Message Board Network

DLE · 12-29-2002, 11:59 PM

HEY GUYS NICE BOARD JUST A FEW ?S ON GAS MILAGE
I HAVE A 95 WITH A 350 IT GETS 16MILES PRE GALLON OK I DON'T THINK THAT IS BAD..

MY FATHER INLAW HAS A 85Silverado WITH A 305 RUNS GREAT HAS ABOUT 90.000 ON THE CLOCK BUT DOAEN'T USE OIL STILL STRONG BUT SUCKS THE GAS DOWN BAD ,HE HAS NEW PLUGS
CAP ROTOR ,,,NOT SURE ABOUT THE WIRES BUT HE GETS ABOUT 8/9 MILES IS THIS NORMAL FOR THIS YEAR TRUCK???
MAN IT IS A VERY NICE CLEAN TRUCK WOULD LOVE TO BUY IT SOME DAY I KNOW IT WILL NEED A REBUILD BY THEN
ANY INPUT ON THE MILAGE WOULD BE A GREAT HELP.
THANKS ..
SORRY NOTICED I HAD CAPS ON...

bigblock73 · 12-30-2002, 12:09 AM

The 82 I had with a 305 was getting me about 15 MPG, I think 8/9 miles a gallon is not very good for a tuned up 305.

What kind of gears are in back, lower gears (higher numerically) would give you lower MPG but I don't think it would drop it THAT low.

Sounds like the carb may be hosed and in need of a rebuild...or new one altogether.

-Jeff

DLE · 12-30-2002, 12:16 AM

hey bb73 the rear is stock I know that dose not help much..
I'm may sound stupid here as far as the carb I belive it has a tbi..
dose that sound right...

low 84 · 12-30-2002, 12:22 AM

if its all original then its carbed and has a Q-jet. they didn't start putting tbi in untill 87. has someone swaped it to an 87 and up motor with tbi?

**swervin ervin** · 12-30-2002, 12:23 AM

Hey DLE, and welcome.

No, 85 305's had a Q-jet carb. And I agree with Jeff, 8-9 mpg sucks. I also agree it sounds like the carb may need some attention.

BTW, TBI didn't come on trucks until 87.

DLE · 12-30-2002, 12:35 AM

HMMMM thanks for the help I thought it was a 85 ok if someone did a swap or say it is an 87 with the tbi /what can he look for to help out the milage i do know it has the tbi but I may be wrong on the year.
thanks again

DAVID

gchemist · 12-30-2002, 07:33 AM

I get 16-18 in the city with a 305/700R4 tranny with 3.08 gearts. 17-19 on the highway. I would definately start looking into the problem.

MylilBowTie · 12-30-2002, 10:53 AM

I get 4 mpg!! whooo hooo... time to start looking for a good working Q-jet with some slight modifcations. Still need some gears and a small stall convertor. 2.73 gear and 32s right now.

PHOENIX · 12-30-2002, 12:33 PM

MPG = 11 - 14

Stock 350 w/ granny 4 speed.

ocbaud · 12-30-2002, 12:39 PM

i get 8-9 mpg with mine

i need a new carb too

solidaxel · 12-30-2002, 01:13 PM

11 city 14 hwy 3.42 28" tires 78 350 148K all stock

*1FaastC10* · 12-30-2002, 02:11 PM

Quote:

Originally posted by MylilBowTie
I get 4 mpg!! whooo hooo... time to start looking for a good working Q-jet with some slight modifcations. Still need some gears and a small stall convertor. 2.73 gear and 32s right now.

screw the carb, put the gears in first, and you may not even need the converter.

DLE · 12-30-2002, 05:07 PM

HEY THANKS FOR THE HELP I STILL DON'T KNOW WHERE TO TELL
HIM TO CHECK NEXT..
NEW
PLUGS
CAP
ROTOR
RUNS GREAT STILL SEEMS TO HAVE PLENTY OF POWER
MAYBE A NEW SET OF PLUG WIRES..???I DUNNO
THANKS AGAIN

HAPPY NEW YEAR

solidaxel · 12-30-2002, 05:46 PM

Changed the Air filter lately !!!!

85Silverado · 12-30-2002, 05:59 PM

I get horrible gas mileage too, but that might be the hole in the tank too...hehe But I know shes running rich....I was putting on the plates my eyes watered right up and stung and i checked the plugs and they're wet....so I think I'm in the same boat with the carb rebuild. I was thinking about going with a Road demon jr...i don't think i'd need more then 600cfm for a stock 305? and edelbrock sells a adapter to but a squarebore onto a spreadbore...any thoughts?

Hooter · 12-30-2002, 08:21 PM

my 77 silverado with 4.10's and a 400sb I manage to get 15mpg with it on the highway

gchemist · 12-30-2002, 08:38 PM

Check for a collapsed cat. They can sure kill gas milage. What kinda oil is he using? Check the fuel lines for leaks at the pump and the tank switcher. Holes in tanks is a common problem too.

DLE · 12-31-2002, 01:08 AM

THANKS great tips never thought of that..yeah the darn cat
you could be on to something there.
as far as leaks it is garage kept and he would notice that.
as far as oil i will ask him...

arveetek · 12-31-2002, 11:07 AM

I don't drive vehicles with carburetors anymore.....I prefer injection pumps!

Diesel, man! It's the only way to go. I get 18.5 mpg average in a 3/4 ton truck w/4.10 gears!

I actually broke 19.5 mpg a couple of weeks ago. Hadn't done that for a while. I used to get a consistent 20 mpg or better when I had 3.42 gears, and before I "tweaked" the motor a bit.

Don't forget when talking about fuel mileage, that rear end gear ratio, transmission type, and tire size are just as important as any other factor. A truck with 2.73 gears, an overdrive tranny, and large tires will usually get twice the mileage as another truck with a three-speed, 3.73/4.10 gears, and small tires, even if both trucks have the same exact engine.

12-29-2002, 11:59 PM	#1
DLE Registered User Join Date: Apr 2002 Posts: 16	Gas Milage HEY GUYS NICE BOARD JUST A FEW ?S ON GAS MILAGE I HAVE A 95 WITH A 350 IT GETS 16MILES PRE GALLON OK I DON'T THINK THAT IS BAD.. MY FATHER INLAW HAS A 85Silverado WITH A 305 RUNS GREAT HAS ABOUT 90.000 ON THE CLOCK BUT DOAEN'T USE OIL STILL STRONG BUT SUCKS THE GAS DOWN BAD ,HE HAS NEW PLUGS CAP ROTOR ,,,NOT SURE ABOUT THE WIRES BUT HE GETS ABOUT 8/9 MILES IS THIS NORMAL FOR THIS YEAR TRUCK??? MAN IT IS A VERY NICE CLEAN TRUCK WOULD LOVE TO BUY IT SOME DAY I KNOW IT WILL NEED A REBUILD BY THEN ANY INPUT ON THE MILAGE WOULD BE A GREAT HELP. THANKS .. SORRY NOTICED I HAD CAPS ON...

12-30-2002, 12:22 AM	#4
low 84 Registered User Join Date: Jan 2002 Location: Houston, TX Posts: 2,144	if its all original then its carbed and has a Q-jet. they didn't start putting tbi in untill 87. has someone swaped it to an 87 and up motor with tbi? __________________ '51 F100, backhalf with a narrowed 9 and coil overs, 18.5" mickeys, monte front clip, +400" sbc in the works '05 1500 Crew Cab RIP '84 swb 5/7 drop, solid cammed 408 w/ fully ported dart heads, th350 w/ 10 inch hughes, 12 bolt w/ 3.73 richmonds and a locker '80 swb 4x4 in progress: 7" lift, 350 th350/np205, d44 and 1.5" ORD tie rod, 14BFF w/discs , armored diff covers, 40" MTR's

12-30-2002, 12:23 AM	#5
swervin ervin You get what you pay for Join Date: Dec 1999 Location: Cherryville, NC Posts: 4,798	Hey DLE, and welcome. No, 85 305's had a Q-jet carb. And I agree with Jeff, 8-9 mpg sucks. I also agree it sounds like the carb may need some attention. BTW, TBI didn't come on trucks until 87. __________________ Mike 1985 Chevy C-10

12-30-2002, 07:33 AM	#7
gchemist BAD BOW-Silverado XST Join Date: May 2000 Location: Senior Member from Austin, TX Posts: 6,431	I get 16-18 in the city with a 305/700R4 tranny with 3.08 gearts. 17-19 on the highway. I would definately start looking into the problem. __________________ Gerardo a.k.a. Mad Chemist Silverado XST videos

12-30-2002, 10:53 AM	#8
MylilBowTie Right turn Clyde Join Date: Nov 2002 Location: Cincinnati, Ohio Posts: 2,911	I get 4 mpg!! whooo hooo... time to start looking for a good working Q-jet with some slight modifcations. Still need some gears and a small stall convertor. 2.73 gear and 32s right now. __________________ 1974 C25 LWB: 454 4bbl Carb / TH400 / 3.73 1992 Camaro RS 305 TBI

12-30-2002, 12:09 AM	#2
bigblock73 yeller Join Date: Oct 2001 Location: Twin Cities Posts: 13,826	The 82 I had with a 305 was getting me about 15 MPG, I think 8/9 miles a gallon is not very good for a tuned up 305. What kind of gears are in back, lower gears (higher numerically) would give you lower MPG but I don't think it would drop it THAT low. Sounds like the carb may be hosed and in need of a rebuild...or new one altogether. -Jeff

12-30-2002, 12:16 AM	#3
DLE Registered User Join Date: Apr 2002 Posts: 16	hey bb73 the rear is stock I know that dose not help much.. I'm may sound stupid here as far as the carb I belive it has a tbi.. dose that sound right...

12-30-2002, 12:35 AM	#6
DLE Registered User Join Date: Apr 2002 Posts: 16	HMMMM thanks for the help I thought it was a 85 ok if someone did a swap or say it is an 87 with the tbi /what can he look for to help out the milage i do know it has the tbi but I may be wrong on the year. thanks again DAVID

12-30-2002, 12:33 PM	#9
PHOENIX Registered User Join Date: Oct 2002 Location: Phoenix, Arizona Posts: 4,703	MPG = 11 - 14 Stock 350 w/ granny 4 speed. __________________ * AVOID: LOPER'S PERMORANCE / LOPERSPEED.COM OF PHOENIX, AZ & COTTMAN TRANSMISSION *

12-30-2002, 12:39 PM	#10
ocbaud Garage Queen Material Join Date: Oct 2002 Location: USA Posts: 4,129	i get 8-9 mpg with mine i need a new carb too

12-30-2002, 01:13 PM	#11
solidaxel Registered User Join Date: Dec 2002 Location: Cactus Patch So. Az Posts: 4,749	11 city 14 hwy 3.42 28" tires 78 350 148K all stock __________________ 53 TuTone Extended Cab 350 4-Spd 3:08 (SOLD) 53 Chevy Moldy pearl green ZZ-4 4L60E 9" 3:25 55 GMC 1st Black Mll (ZZ4) ZZ6 TKO 600 5 sp 3:73 62 Solidaxle Corvette Roman Red (327 340hp 4spd 3:36) C4 & C5 suspension tube chassis LS 3 4L70E 65 Corvette Coupe 327 350hp 4spd 4:11 78 Black Silverado SWB (350/350) 5.3 & 4L60E 3:42 2000 S-Type 3.0 (wife cruiser) 2003 GMC SCSB 5.3 4L60E 3:42

12-30-2002, 05:07 PM	#13
DLE Registered User Join Date: Apr 2002 Posts: 16	HEY THANKS FOR THE HELP I STILL DON'T KNOW WHERE TO TELL HIM TO CHECK NEXT.. NEW PLUGS CAP ROTOR RUNS GREAT STILL SEEMS TO HAVE PLENTY OF POWER MAYBE A NEW SET OF PLUG WIRES..???I DUNNO THANKS AGAIN HAPPY NEW YEAR

12-30-2002, 05:46 PM	#14
solidaxel Registered User Join Date: Dec 2002 Location: Cactus Patch So. Az Posts: 4,749	Changed the Air filter lately !!!! __________________ 53 TuTone Extended Cab 350 4-Spd 3:08 (SOLD) 53 Chevy Moldy pearl green ZZ-4 4L60E 9" 3:25 55 GMC 1st Black Mll (ZZ4) ZZ6 TKO 600 5 sp 3:73 62 Solidaxle Corvette Roman Red (327 340hp 4spd 3:36) C4 & C5 suspension tube chassis LS 3 4L70E 65 Corvette Coupe 327 350hp 4spd 4:11 78 Black Silverado SWB (350/350) 5.3 & 4L60E 3:42 2000 S-Type 3.0 (wife cruiser) 2003 GMC SCSB 5.3 4L60E 3:42

12-30-2002, 05:59 PM	#15
85Silverado Registered User Join Date: Dec 2002 Location: Milwaukee, Wisconsin Posts: 198	I get horrible gas mileage too, but that might be the hole in the tank too...hehe But I know shes running rich....I was putting on the plates my eyes watered right up and stung and i checked the plugs and they're wet....so I think I'm in the same boat with the carb rebuild. I was thinking about going with a Road demon jr...i don't think i'd need more then 600cfm for a stock 305? and edelbrock sells a adapter to but a squarebore onto a spreadbore...any thoughts? __________________ Paul D. '78 C20 Scottsdale 350ci 3 speed with granny gear 14 bolt rearend My trucks are "Car-Guy safe".......which pretty much means death trap in the hands of a normal civilian.

12-30-2002, 08:21 PM	#16
Hooter My other Love Join Date: Aug 2001 Location: Castlegar B.C. Canada Posts: 4,085	my 77 silverado with 4.10's and a 400sb I manage to get 15mpg with it on the highway __________________ Castlegar B.C.The great white North (Canada Eh!) Hooter_5@hotmail.com First generation Monte Carlo club pictures of my life



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12-30-2002, 08:38 PM	#17
gchemist BAD BOW-Silverado XST Join Date: May 2000 Location: Senior Member from Austin, TX Posts: 6,431	Check for a collapsed cat. They can sure kill gas milage. What kinda oil is he using? Check the fuel lines for leaks at the pump and the tank switcher. Holes in tanks is a common problem too.

12-31-2002, 01:08 AM	#18
DLE Registered User Join Date: Apr 2002 Posts: 16	THANKS great tips never thought of that..yeah the darn cat you could be on to something there. as far as leaks it is garage kept and he would notice that. as far as oil i will ask him...

12-31-2002, 11:07 AM	#19
arveetek Ultimate Diesel Dude Join Date: Oct 2002 Location: Southwest Missouri Posts: 328	I don't drive vehicles with carburetors anymore.....I prefer injection pumps! Diesel, man! It's the only way to go. I get 18.5 mpg average in a 3/4 ton truck w/4.10 gears! I actually broke 19.5 mpg a couple of weeks ago. Hadn't done that for a while. I used to get a consistent 20 mpg or better when I had 3.42 gears, and before I "tweaked" the motor a bit. Don't forget when talking about fuel mileage, that rear end gear ratio, transmission type, and tire size are just as important as any other factor. A truck with 2.73 gears, an overdrive tranny, and large tires will usually get twice the mileage as another truck with a three-speed, 3.73/4.10 gears, and small tires, even if both trucks have the same exact engine. __________________ Project truck: '81 C/20 converted to 6.2L TURBO DIESEL bored .040", gear drive, 6.5L injectors/pump, custom pistons, custom 4" exhaust, 700R4, 4.10's Daily Driver: '95 K1500 Tahoe, 6.5L TURBO DIESEL, NP241, 4L80E, 3.42's

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