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MGB expected MPG?

Posted by n56545 
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29desoto Avatar
Wayne Sanders
Outside Otis, OR - in the woods!, USA   usa
1953 MG TD
1965 MG MGB V6 Conversion "Carmine"
1977 MG MGB "Ole Yeller"
1979 MG MGB "Kermit" ~ For Sale ! ~    & more
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
(TD 4288)

"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.

53 TD Mark II - a work in progress.

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
RK Muenchausen
PC, Oregon, USA   usa
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

MGB GT cutaway car photos site by Paul Hunt can be found here >>>

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

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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.

Fairfield, CA, USA   usa
I'd say a realistic range would be 18-35.

anything much over 25 I'd suspect of bad records/calculation or heavy highway miles.

a heavy foot shows up more prominently with the B. And it seems a lot of folks seem to believe one must keep the tach needle between 4 and 6 at all times.

And city driving also drags it down further than a modern car would see.

1973 Pale Primrose Roadster. A nice 10-footer!
SUs, Datsun 5-speed

Jim K Avatar
James A. Krasnansky
Liberty, KY, USA   usa
1970 MG MGB GT "Chloe"
1971 MG MGB GT "Roscoe"
1972 MG MGB "Camilla"
I bought a '70 GT in 2010. I put 12,000 miles on it in a year. Mid-grade fuel, HS4's, OD. I average about 28 - 32 mpg. Got 36 on a couple 700 mile runs with OD on the Interstate. This '70 is the best running MG out of the 6 I've had.

Jim K is a grease-stained wretch

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Monte johnjulio
Greensboro, North Carolina, USA   usa
1967 MG MGB GT "Toaster"
1974 MG MGB "The B"
1979 Triumph Spitfire 1500 "Shitfire"
If properly tuned:

Ethanol fuel will reduce your mileage 8-15%

Tire under-inflation can also affect it as can thicker viscosity oil.

Also how you drive is important. holding in a lower gear too long can really pull down your mileage but shifting too soon and lugging the engine can do the same.

I averaged 27-32 with my roadster over a 10 year period using straight 50wt oil.

My GT has averaged around 26-28 over the last 1000 miles though I do have some more fine-tuning to do.

Neither car has overdrive.

"...They say that a man with two restoration projects is a poor man...I now have three...WTF was I thinking!?!?!?!?!?!?!"

1967 MGB-GT,1979 MGB roadster, 1979 Triumph Spitfire 1500 1974 MGB Roadster (retired, giving its life to be a parts car)

My 1974 MGB restoration at:
My 1979 Spitfire restoration at:
My 1967 MGB-GT restoration at:

Tom D
Cape May, USA   usa
my 71 with 32/36 weber non o/d pertronix ig, new plugs/wires/cap & rotor about 22mpg overall average--rebuilt head, new oilpump and premimum fuel .. most rides 50 miles or under, some 100 milers..I keep stabil in all my fuel as todays gas deteriates if it is not used within about 2 weeks of purchase.

Mike Keeney
scenic Fleetwood PA, USA   usa
1976 MG MGB
I figure on 18mpg as my average. 76 B, twin HS4 with AAA carb needles, desmogged, performance cam, no OD, I don't drive like an old man, it is for fun.

Fairfield, CA, USA   usa
the only time I have ever seen premium fuel to deliver greater mileage was when I had a SAAB that would advance timing until it pinged and then back off. High test got about 10% better over about 5,000 miles.

Never saw that on any other car. Including the MG. The only way consumption would be affected is driving parameters or active engine tune adjustment and the B doesn't have the latter as the SAAB did.

It is true that if the car is having (perhaps unrecognized) detonation, then premium would probably reduce/eliminate that and that would affect mileage to the good. But that means the state of tune was inappropriate for the fuel. Correcting this should change the matter considerably.

1973 Pale Primrose Roadster. A nice 10-footer!
SUs, Datsun 5-speed

cdaubs Avatar
Charlie Daubs
Redding, California, USA   usa
1964 Jaguar E-Type "Snowball"
1970 MG MGB
My '70 got 30mpg when I drove it home from Las Vegas to Redding. A trip of over 800 miles. Not really sure how many miles are on it since it has been through a couple of owners and the speedo has turned over and the cable is now broken. But I think with proper tuning, good gas, and a light to moderate foot, you should get something close.

ShickenChit Avatar
Toby Foster
Danville, CA, USA   usa
19.5mpg overall, Weber DGV 32/36, wider than normal "boy racer" Civic tires, 5 speed tranny, "hot street cam," California gas. I've never really messed with my timing, as my timing light died, and it seems to run fine except for being consumptive.

jim jensen
cleveland, USA   usa
...check the plugs.....and the points.......if plugs are black, then adjust the carbs......or go to ngk bp5 if fawn colour- to heck with it.....just enjoy the car........most here can afford a few bucks in gas.....

ourmg Avatar
George Heissenberger
Victor, New York, USA   usa
1973 MG MGB "Parts"
1973 MG MGB MkIII "OUR MG- The Old Girl"
2006 Mini Cooper "Greta's Mini"
2014 BMW MINI Countryman ""Maxi""
1973 desmogged MGB with stock SU HIF's and I get 25-27 MPG like clockwork - have for decades.

"OUR MG" Glacier White 1973 MGB, owned since 1983. Factory hardtop. Member MG Car Club Western New York Centre
"Beer is proof God loves us and wants us to be happy" - Ben Franklin

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