MGB & GT Forum

Welcome! Sign In Register
Please Sign In or Register to Search

MGB expected MPG?

Posted by n56545 
n56545 Avatar
Rusty Mayes
Vacaville, California, USA   usa

After owning and driving my 67GT for eight months and some 500 miles, Mostly country road and town in town driving, I am averaging about 15 miles per gallon fuel burn. Is this typical or should I be looking for a carb or ignition problem? I recently found the timing advanced some ten degrees. The engine seems to run fine and have pleny of power. I am planning on an overhaul shortly because of age and low oil pressure. I will do the carbs as well. Just wondering what you guys generally get for mileage.
. You can hide this ad & support this site by upgrading to a Gold Membership ~ click here for more info
applebj8 Avatar
Jon Appleby
Lake Wylie, SC, USA   usa
1971 MG MGB

30+ mpg here - re-manufactured engine, 0.020" over, with twin SU's and overdrive...
herculesmgb1971 Avatar
gerard boulanger
Hercules, CA, USA   usa

22-26 MPG with a Weber 32/36 and overdive.



Edited 1 time(s). Last edit at 03/07/2013 07:50PM by herculesmgb1971.
. You can hide this ad & support this site by upgrading to a Gold Membership ~ click here for more info
oily-hands Avatar
Owen Frankland
Stockton on Tees, Cleveland, United Kingdom   gbr
1937 MG TA "Numbum"
1971 MG MGB GT "The Bruise"

I'm avaraging about 25mpg (UK gallon) in mixed driving, and I don't drive it gently. On a run using mostly overdrive top I get around 30mpg.

This seems to be the norm from the people I've spoken to about it.



Member of The International Society of Luddites (Unrepentant Chapter).

Take the time to understand what a part does and how it does it, then you'll have a better understanding of how to fix it when it goes wrong. Beats the scattergun approach every time.

Ignition testing made easy.

Making your MGB handbrake work

My You Tube Channel

Life with an MG TA and an MGB GT in the UK.
the omega man Avatar
phil wilkins
staffordshire, Stafford, United Kingdom   gbr

25 to 30 I reckon
. You can hide this ad & support this site by upgrading to a Gold Membership ~ click here for more info
Delbert Golightly
Spanaway Wash, USA   usa

dang it Rusty.........DON'T EVER rebuild yer engine 'cuz of low gas mileage until you do the dreaded "compression" test. Yer 1.8L engine should consistently gitt about 25-mpg US. Yer carbs are way outta adjustment. While ignition timing and sparkies will effect yer engine economy, ittza yer carbs. Gitt'em ADJUSTED correctly and then complain about mileage .........Dell, yer self-appointed sparkie-meister
aarteinen Avatar
Petri Nieminen
Oulu, N/A, Finland   fin

My '65 Roadster gives me roughly 9 l/100 km or 26 mpg (US) on long haul (when doing more than 300 km w/o breaks) at an average speed of 95 kph (60 mph). 3 synch, non-od, will wear ear protectors ...
. You can hide this ad & support this site by upgrading to a Gold Membership ~ click here for more info
Steve J
SHEFFIELD, United Kingdom   gbr

My '74 BGT with OD gives me 22mpg in town driving and 35mpg on a long run at 50/60mph.
I reckon that equates to around 18mpg and 29 mpg in US gallons.
tomkatb Avatar
Larry Baygents
Dayton, Ohio, USA   usa
1963 MG MGB

Bone stock 63.

22-28 depending on the operator. No overdrive.

Always step one. Verify 100% the correct operation and model number of the dizzy.

Step two. Retest the dizzy.

Fill in the form, takes 10 minutes.

Initial idle advance___
Advance at 3000rpm___
Advance when applying a vacuum to the advance___
Vacuum advance holds with tongue over the hose, yes/no
Dizzy I'd number___
Is advance steady at idle, yes/no

What carb set up?

If everything is as it should be, the carb may be an issue.



L.W.(Larry)Baygents
63B
77 Spit

29desoto Avatar
Wayne Sanders
Outside Otis, OR - in the woods!, USA   usa
1965 MG MGB V6 Conversion "Carmine"
1977 MG MGB "Ole Yeller"
1979 MG MGB "Kermit"
1984 Chevrolet Corvette "The Green Weenie"
1994 Chevrolet S10 "Lil Red"

Looking at the OP, I have a couple of questions -

Driven 500 miles in eight months. Sixty miles per month. Unless the car is gassed up at each run, the gas is old.

Low oil pressure. How low?

Was the car previously driven in a similar fashion? Has it been parked more than driven?

I'm thinking a can of Seafoam and a long spirited drive might be the first step, right after going through Larry's check sheet, and checking the valves.

This may be one gummed up car. IMHO.



Wayne Sanders
Rose Lodge, OR

"I don't care to belong to any club that accepts people like me"-joined Willamette Valley Club in 2011

77 MGB - Four tone paint - some kind of electronic ignition - hood props - cheap tires - new springs all around - mixture of poly and rubber bushings - original exhaust - fuzzy seatcovers - stereo out of old F150 pickup - virtually no rust - right front wrecked and semi well repaired - just about right for me!

78 MGB - Done right by a good PO, and I only bought it. Tell Jim how nice it is. But I did put in a Datsun 5 speed.

79/65 MGB - Carmine- V-6 - T-5
95% Done. V-6 is a treat, and the five speed is great.
More to do, but isn't there always?
Michael74MGB Avatar
Michael Austin
Odessa, TX, USA   usa
1974 MG MGB MkIII "Maggy"

A while back, someone posted up the EPA estimated mileage from an original window sticker from a 1980 model and it was 16mpg! Mine seems to do around 20 in town, and probably upper 20's on the road - maybe a bit more (been a while since I had it on a long highway drive).



74 MGB: APT VP11 cam, lifters, valve springs; 9:1; ported head; TT exhaust; vernier timing gear; wizard aluminum radiator; dizzy by Jeff S.; stock HIF4's; it goes on and on.....
n56545 Avatar
Rusty Mayes
Vacaville, California, USA   usa

A little back ground on the 500 miles in 8 months. I bought the car last summer and tnen life got in the way of getting it in shape to be a daily driver. It had sat for a while before I bought it. I sent it to the upholstery shop as a back burner project which took three months and then after driving it for a week I got into the front end rebuild which took another month to. Driving in between and since then has been sporatic but "spirited" so I am not surprised that the mileage is a tad low. I will do the analysis and tune the carbs and do some more conservative driving and post any improvement, assuming life stays out of the way!
I really appreciate the response guys. This website really makes playing with the LBC a ton of fun. Funny when I was a kid and the car gave me crap I was annoyed. Now I laugh and have a blast correcting what ever comes up.

Attached is a pic of my shop with the spring's projects.

Attachments:
photo.jpg (14.2 KB) –
photo.jpg

oily-hands Avatar
Owen Frankland
Stockton on Tees, Cleveland, United Kingdom   gbr
1937 MG TA "Numbum"
1971 MG MGB GT "The Bruise"

I never noticed the 500 miles. That's nowhere near enough miles to calculate mpg.

You need to fill up and drive, note the mileage and fuel used at next fill up, then repeat at least twice more. That should give you a more accurate figure. You might not be doing as badly as you think.



Member of The International Society of Luddites (Unrepentant Chapter).

Take the time to understand what a part does and how it does it, then you'll have a better understanding of how to fix it when it goes wrong. Beats the scattergun approach every time.

Ignition testing made easy.

Making your MGB handbrake work

My You Tube Channel

Life with an MG TA and an MGB GT in the UK.
stuntflyr Avatar
Chris McMillin
Los Angeles, USA   usa

In reply to # 2305530 by n56545 After owning and driving my 67GT for eight months and some 500 miles, Mostly country road and town in town driving, I am averaging about 15 miles per gallon fuel burn. Is this typical or should I be looking for a carb or ignition problem? I recently found the timing advanced some ten degrees. The engine seems to run fine and have pleny of power. I am planning on an overhaul shortly because of age and low oil pressure. I will do the carbs as well. Just wondering what you guys generally get for mileage.

I figure 25 MPG.
"Seems to run fine and have plenty of power", means to me; Drive it more, 300 miles out of a tank is normal once one starts driving more than two tanks a year!
Overhaul for low oil pressure? Below 50 at warm cruise? What kind of oil? What weight?
I'd be driving the heck out of it, going on trips to 150-300 mile distant places and record those performance figures before thinking of making any overhaul decisions. Your choke on and idle periods compared to your total gallons burned could throw your mileage comps way out. You aren't driving it enough to be able to tell.
(Go to the airport and buy 5 gallons of 100LL in a can "for your homebuilt airplane's fuel system calibration" and see how it acts after driving that tank through it! Or just add a gallon to each tank, you'll see an improvement. Cali gas alcohol and additives penalties to performance really change when TEL is added to the old GB series engine. Also ask where there are any no alcohol MoGas pumps, airplanes are allowed to use auto gas with no ethanol or additives if they have the approved paperwork and this is good gas for the MGB too. You can lean the SU's out, if you're over say 2500 feet a lot, by a flat and get some better mileage too, but if it "fine" and "powerful" I wouldn't mess with success.)
Chris...
EmgesMG Avatar
Robert Emge
Red Bluff Ca., USA   usa

My '71 GT gets about 26mpg on regular(87 octane), and about 28mpg on "premium"(92 octane) goes over 30mpg on Nevada premium, if I keep it around 70mph cruising. Stock motor with 90K with OD.
29desoto Avatar
Wayne Sanders
Outside Otis, OR - in the woods!, USA   usa
1965 MG MGB V6 Conversion "Carmine"
1977 MG MGB "Ole Yeller"
1979 MG MGB "Kermit"
1984 Chevrolet Corvette "The Green Weenie"
1994 Chevrolet S10 "Lil Red"

Looking at your shop, I wonder that you need to ask us questions! Looks to me like you are well into the hobby/addiction!

I was thinking that you might be a young guy expecting these LBC's to put out the mileage of a Honda Civic or something.

Someone at a gas station recently asked me if I got 45 MPG out of my 77 "B". I assured them that I did not.



Wayne Sanders
Rose Lodge, OR

"I don't care to belong to any club that accepts people like me"-joined Willamette Valley Club in 2011

77 MGB - Four tone paint - some kind of electronic ignition - hood props - cheap tires - new springs all around - mixture of poly and rubber bushings - original exhaust - fuzzy seatcovers - stereo out of old F150 pickup - virtually no rust - right front wrecked and semi well repaired - just about right for me!

78 MGB - Done right by a good PO, and I only bought it. Tell Jim how nice it is. But I did put in a Datsun 5 speed.

79/65 MGB - Carmine- V-6 - T-5
95% Done. V-6 is a treat, and the five speed is great.
More to do, but isn't there always?
OldBloke Avatar
Jim Legg
Napa, California, USA   usa
1970 Rover 3500
1971 MG MGB GT
1972 MG MGB V6 Conversion
1973 MG MGB "Tagalong"

My '71 never saw more than 16-18 around town, but hwy driving with O/D saw consistent 26-30 MPG. (Always premium gas)



"Not all who wander are lost." -J.R.R. Tolkien
bobmunch Avatar
Bob Muenchausen
PC, Oregon, USA   usa
1968 MG MGB GT "Traveler"

Just statistics to corroborate what may have already become the consensus:

Stock 1968 18GF engine/cam/valves (all smog gear except PCV valve removed)
Stock HS-4 carbs / #5 needle
Jeff Schlemmer stock distributor, Crane XR-700 electro-optical points substitute and Lucas Sports coil.
NGK BP6ES spark plugs (plugs as shown below 1 to 4 , L > R )
Regular gas (Oregon-10% ethanol)



Around Town - 26-28 mpg
4th gear open road 30 mpg
O/D on interstate 32-34 mpg



"All that my contradictory experiences demonstrate, sometimes, is that things and materials don't always follow the course of our commonly accepted thinking about them, but end up sometimes besting our knowledge of them."


SU Carb setup instructions ~ You don't need smog gear to need/use these factory instructions.
>>>https://www.dropbox.com/s/dgjgbxszv1h22hy/MG%20EMISSIONS%20MANUAL.pdf

MGB GT cutaway car photos can be found here >>> http://www.cibolas7.net/resources/cutaway.htm

A thorough guide to rubber rotary seals as used on your crank, axles, etc >>> http://www.rlhudson.com/Shaft%20Seal%20Book/index.html



Edited 3 time(s). Last edit at 03/06/2013 12:18PM by bobmunch.

Attachments:
04 2012 plug reading .jpg (32.5 KB) –
04 2012 plug reading .jpg

crashbash Avatar
david bash
Saint Charles, Missouri, USA   usa

I don't remember the exact numbers but I do know it was cheaper to run premium fuel rather than regular. Tested it several times, Tuned engine to each fuel and figured cost per mile
Clay Johnston
Mt. Olive, MS, USA   usa
1972 MG MGB

My 72 w HC/fast road cam/HS4s/OD, I average about 27USmpg per tank. I tune my car over several tanks of gas. If its consistently under 27, I'll check plugs and lean the mixture.

As I've said before, if you put a group Bs on a exhaust analyzer, you would find many running rich. I know I was surprised by what the sniffer reported.
. You can hide this ad & support this site by upgrading to a Gold Membership ~ click here for more info

Reply to this topic or post your own questions!

Members Sign In if you've already registered, or

Register a New Account

Registration is free and takes less than a minute

Having trouble posting or changing forum settings?
Check the Forum Help File (FAQ) or contact the webmaster.


Join The Club

Sign in to ask questions, share photos, and access all website features

MGExp Menu

What's New

Membership

Forums ->

MGB & GT

MG Midget

Buy, Sell & Trade

Vendor Market

MG Engine Swaps

Original MG

MGA

MGC

MG Magnette

1100 & 1300

T-Series & Prewar

Modern MGs

MG Motorsports

Member Meetup

MG 2015 Event

Other Vehicles

Off Topic

Clubs

Forum Search

Random Topic

Latest Posts

Live Chat

Calendar

Journals

Tech Library

Car Registry

Cars For Sale

Model Info

Motorsport

Directory

Member Map

MGExp Store

Search Site

Advertising Info

Smartphone quick link
mgexp.mobi

Adjust Text Size

Larger Smaller
Reset Save