2010 tdi jetta 13000 miles when i bought it last month. kept in garage. seller said he got 45 mpg . car was used very little. I get 30 to 35 miles pr gallon. every body I talk to gets 45 to 50 miles per gallon even 10 year old vw diesels. vw dealership says everything checks out ok. at 70 miles per hour , tach is at 2400rpms.
poor diesel mileage on 2010 Volkswagen Jetta TDI
by joegasperino in Merritt Island, FL on August 02, 2013
ANSWER by Karmakanix on November 29, 2014
Simple stuff would be air filter restricted. Very low tires? 6 speed transmission or automatic DSG? No check engine light (MIL)? Most causes would also turn on the check engine light.
Oil and carbon tend to build up, creating restrictions in the intake manifold. Symptoms will be loss of power (sometimes severe) and poor fuel economy.