I change my filters and oil every 4 months. For the price they cost it's stupid not to. Over here the whole filter kit, oil filter + air filter + fuel pre filter and spin on fuel filter are less than $18.

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1992 Mercedes 190D 2.5 turbo 5sp manual. EGT+boost gauges. Boost controller set to ~14.5 psi. 1 1/4 turns on full load adjustment. LPG injection. Next in the list is water injection.