I recently took my 1980 300SD on a 3600 mile trip and it ran perfect. However, it got only 23 MPG. It seems to have good power, used about a liter of oil (castrol Syntec), starts instantly every time and doesn't smoke.
I adjusted the valves and checked the cam timing (3 degrees late) before I left.
What can I do to increase the mileage to the 28 MPG it should get?

Drive real slow!! . You're doing pretty good at 23 per. How many miles on the car??

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Jeff L
1987 300e
1989 300e
1987 BMW 325

28's not bad. I see around 28-30 from my '80 300SD even with a VERY heavy right foot. By the way, if you think your engine is up to it, find a nice, straightaway on the interstate and mash it, wind that tach around to 4,800rpm and feel how wonderful a W-116 is at 110mph--and man, the growl of that engine....

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Rgds,
Aaron Greenberg
MB technician
Precision Motorcars, Cincinnati, Ohio
'67 250SE Cabriolet
'77 450SL
'80 300SD
'85 380SE
'89 420SEL
'93 300E 2.8
'72 Alfa Romeo 2000GTV
'74 Jensen Interceptor Mk.III
'81 DeLorean DMC12

Aaron: I get only 23 MPG not the 28 I should get and that you get on your 300SD. What can I do to increase the milage on my 300SD? It has 180K miles but runs just about perfect except for the excess fuel consumption.

quote:

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Originally posted by P.E.Haiges:
Aaron: I get only 23 MPG not the 28 I should get and that you get on your 300SD. What can I do to increase the milage on my 300SD? It has 180K miles but runs just about perfect except for the excess fuel consumption.

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There aren't a lot of cheap repairs here. Injectors can be improved with additives but a new set will buy a lot of fuel.

One area thats cheap is the boost signal and of course boost itself. You should measure the boost after the overboost protection switch-over valve. Measure it between the valve and the injection pump. It should max at about 10psi. If you don't get good power you won't get good mileage.


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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician