Ive had two 2.5t w124 -- a 93 and a 92. I drove the 93 a long time and it got 35 mpg pretty regularly. It didn't have egr blocked off but had the Alda removed.

The 92 I have now I haven't driven much cause reverse is out but it got under30 mpg on the way home from illinoise. It has the egr blocked off. I wonder if with the egr blocked and airflow is getting restricted like mentioned it is starving for air. This sounds like a fun easy experiment. I'll give it a try when reverse is fixed.

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What Would Rudolph Do?
1975 300D, 1975 240D, 1985 300SD, 1997 300D, 2005 E320 , 2006 Toyota Prius