I checked mine not too long ago and get about 21 mpg city and 24 highway. The highway was on a trip reaching 80 many times if not staying around there, and the city was just city. Should i maybe pull my injectors and disassemble them to clean them up? Even after my car is hot and is shut off, I can go to restart it right away and it canks for about 15 seconds. Would that be injectors or IP timing? I am talking about the '79 SD.
Thanks
David

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2000 Honda Accord V6 137k miles

1972 300SEL 4.5 98k miles

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My SDL takes a few seconds of cranking when it's hot if I don't preglow first.

My economy has also been similar to yours... about 22 city, 24 highway (window sticker says 22/23). I will wait and see how it does on summer fuel before I get worried about it.