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MG MGA - Mileage

Has anyone added a 5-speed or over-drive and tested their mileage against what they got with the standard 4-speed? Or is there any other reliable information on the effect on mileage of a fifth gear or overdrive?
Steve
Steve Meline

It depends on how you drive the car. I average about 23 mpg. Then again, I have a Judson Supercharger and a LEAD foot. Prior to that it seems I got 24-25 mpg. If I am going to a car show and doing a long drive on the freeway, then my milage goes up to about 26-28 using the cruise control. I also have a 3.9 rear end.
JEFF BECKER

Ask me again next year. I'm planning to add a D-Type overdrive to my MGA gearbox at some point. The parts are mostly sitting here but I don't have the time or expertise to put it all together.
Steve Simmons

Hi I have 1950 cc and 5 speed sierra box and get 25 mpg but I don't drive it hard at all



gordon
g c pugh

should have added the diff is 3.9 ratio
g c pugh

Steve

I have been keeping a very accurate log of my mileage over the last 2 years. However, it has all been with the 5-speed box so I have no comparison data to the 4-speed box. The average consumption since 23 March 2006 is 21.69mpg, with a top individual tank load of 27.3mpg and a low of 18.84mpg. In the last year I have been also running the 3.9 diff and this has seen an average fuel improvement of about 1mpg, but this has been mainly on short runs (commuting) of about 4 miles. A longer run I did the other day of 190 miles showed a significant improvement on the current tank load of what looks like an additional 7mpg. Normally I have to refuel every 200 miles. After this run the tank was still showing half full so I should get about 270 miles out of it (indicator drops fairly quickly on my car once below half).

Steve
Steve Gyles

I get about 25 mp(imp)g with my 1500 and close ratio box. It does vary a bit depending on the roads.

Steve, let us know how you get on with your D-type overdrive as I'm considering getting one for my Magnette.
Dan Smithers

Just to add a data point for a 4-speed MkII with standard 4.1 rear, stock 1622cc with SU's, standard coil and points (vs. Pertronics) with 93 octane for petrol.

I've checked just about every tankfull over the last 3 years but haven't written them down, so I can't give an overall average. The worst tank was 19 mpg and the best 31. The 31 was a straight, 60-65 MPH run along RT-81 on the way back from Gatlinburg - in rain all the way so it kept my speed down. I find most refills where I've been taking small 5-10 mile trips and letting the car sit for a few days result in 20 - 21 mpg. I think part of the lower mileage is the fact the float bowls evaporate out between starts.
- Ken
Ken Doris

With a 1622 engine, stage 2 B head and the Judson, stock gbx and rear end, I have to refuel every 200 miles.
dominic clancy

Dominic

Great comfort to know that I am not alone. I suspect that a lot of owners have greatly inflated (optimistic) views of their fuel consumption. It is only when you measure it accurately over several months (or years) that you get the true picture. Many drivers talk in generalisms about a tank load of fuel giving them 30 plus mpg. It is only when you measure those tank loads accurately back-to-back that the true figure emerges, and it is usually far lower than you imagine.

I guess I am very sad, but I run a spreadsheet for my fuel consumption. I always fill the tank to full and note the mileage. Over time, the small inaccuracies of exactly how 'full' the tank is filled is of very minor significance. On the plus side, a very low consumption figure last year (16mpg) caused me to investigate and I discovered a leak.

Steve
Steve Gyles

I can't speak of 5-speed or other mods. My useage is now Sunday drives in farmland. My car is a bone-stock 1500 with std 4-speed and 4.3 rear. I get 25-27 mpg ecvery time I fill up. I haven't given it a tune up since I rebuilt it 10,00 miles ago. Time for a points/plugs/valve adjustment etc. in the Spring when she comes out of storage. Oh yeah, I have always run midgrade (91 octane).

I have gotten as high as 28/29 on the highway (70mph +) with the top down and a duffel bag on the luggage rack. Probably could have been higher if I was trying to maximize the fuel economy.

I am surprised that the 5-speeds are not getting better than Dan or I. Maybe it is driving style. I would expect the lower engine RPMs,no matter haw you get there (3.9 or 5-speed) should do better, no?

Chuck
C Schaefer

Last spring I updated my MkII to a 5-main MGB motor and LH overdrive (both from a 1974 MGB). I'm still sorting out the minor glitches, just switched to a pertronix flamethrower for example (big improvement) but mileage seems to be the same as the old 1622 setup. Same SU carbs as before. 18mpg around town, 28 mpg on the highway. But what a pleasure cruising at 70mph and 3100 rpm.

I did try a Weber DCOE, and it delivered a big performance boost but equally big hit in gas mileage. Never was able to get the Weber to run smooth so I switched back.
Jim P

This thread was discussed between 16/11/2007 and 17/11/2007

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