I was wondering what the gas mileage for the 1986 740 diesel was. I am thinking of converting my 1988 Turbo because I've been averaging around 22 mpg and that is starting to add up. If I did decide to convert, how much work would be involved?

I get about 36 MPG mixed road driving with my T-diesel with the air on. I have the 4+E manual transmission in a 764GLE with all the toys.
If you are going to do the conversion and have a donor car I would say go for it however if you are going to start raw meaning drop in a motor and go I have to say STOP! The transmission bellhouse pattern is diffrent along with the engine wiring harness. If you are dealing with a manual transmission you will have to convert over to a cable clutch if yours is presently a hydraulic. Fuel tank is completly diffrent with half of it inside the trunk and you will have to remove the cat. Additional expenses will be for radiator hoses, head gasket and bolts (mandatory) and a new timing belt.
I dont know how integrated the electronics have become for the 1988 model year but I suspect you are going to have a small wiring headache in your future. Maybe that angle will be easy I dont know but having done all the mechanicals on my turbo-diesel from the ground up I do know that you have nothing under your hood that will be compatable with the diesel other than the radiator. Is the 1988 equipped with hydraulic engine mounts? Is the crossmember even compatable with the older rubber mounts I dont know.

You would be better off looking for an older 700 series diesel on Ebay than trying to convert your present car. Even a non turbo 200 series car gets good miles however they are gutless. Do not even think about adding a turbo to a non-turbo block unless you like siezed pistons, been there done that! Turbo blocks have piston cooling jets located on the main oil gallery that spray up to cool the pistons and provide additional oil. Additionaly the turbo block has an oil to water heat exchanger, the non turbo block is not machined to accept the aluminum adapter that carries the filter and cooler. Last but not least the non turbo injection pump does not have the boost fuel control diaphram, if your injection pump is on the low side non turbo you will gain nothing, if its adjusted high you will accelerate hard for a short time while your piston lands crack and the ends of the glow plugs burn off. I speak from unfortunate experience on this one.

Im a diesel nut and most of my past cars have been diesel powered in one way or another. Most people say I crazy but what the heck I earned that title when I stuffed an oldsmobile 5.7 diesel into a 245 wagon and made it work! The car is still on the road and rusted to the door handles!

Badge988 (yawn)

Bage,

I need your address to send the stuff. george.holmer@ttsservices.co.uk
--
George Holmer, Belgium, Europe, 1987 745 GLE Turbo Diesel Intercooler (D24TIC/M46) 200k; 1988 745 Turbo Intercooler (B230FT/M46) 290k; 1988 745 GL (B200E/M47) 190k

You'll spend more money on doing the conversion than you'll
save fuel costs in several years of driving the car. If you
buy a turbodiesel 740 and sell your turbo 740, you'll come
out ahead and not have to worry about doing the conversion.
Plus you'll get to testdrive the diesel prior to spending the
money...
chris

I can easily do 35-40 mpg in my 740 turbo diesel intercooler. There might be differences to the States as mine is a 1987 and I think they did revise then engine somewhat. However, that a diesel should consume as much as the NA car is frankly not true, as you can see I have one of each so I should know. To convert you would need the engine, flywheel and possibly other gearbox stuff, fuel pumps, fuel lines and lots of small bits and pieces. You should get a whole car. The job is technically easy but just hard work. I would intercool the turbo in the process. You should then get a TDI inlet manifold, use your turbo intercooler and possibly manufacture the piping. It will help to make your car quicker.
--
George Holmer, Belgium, Europe, 1987 745 GLE Turbo Diesel Intercooler (D24TIC/M46) 200k; 1988 745 Turbo Intercooler (B230FT/M46) 290k; 1988 745 GL (B200E/M47) 190k

Oh yeah, I am talking imperial gallons.
--
George Holmer, Belgium, Europe, 1987 745 GLE Turbo Diesel Intercooler (D24TIC/M46) 200k; 1988 745 Turbo Intercooler (B230FT/M46) 290k; 1988 745 GL (B200E/M47) 190k

From http://www.fueleconomy.gov:

'86 740 diesel, 4spd auto: 24mpg city/27mpg hwy
'88 740 turbo, 4spd auto: 19mpg city/22mpg hwy

and just for comparison:
'88 740 n/a, 4spd auto: 22mpg city/27mpg hwy

Numbers for manual transmissions will be a little higher.

jeff daigle
'89 745GL 142,000mi (22mpg city/27mpg hwy observed fuel economy)

Whose gallons are we using here? Remember 1 US gallon = 0.833 Imperial gallons. So 27 mpg US = 32 mpg Imp.