Bouth my toyota previa 1999 secind hand. It's an automatic and dual fuel. I mainly drive it on LPG/GPL . One of the cylinders was caracked so had the engine and radiator replaced. Since the engine was replaced instead of doing 120 miles per LPG tank it started doing 50 miles, dropping to 35. Changed the O2 sensor, and it went up again slowly but surely and now does a peak of 80 miles per LPG tank. Checked the air filter but it's new as it was changed when the engine was changed. Took it to a mechanic and everything is fine from emissions. Called LPG mechanic to see if system needed tuning but he told me it was not a problem of LPG system. I have no engine light on but WHY, why is it doing less mileage now then when the engine was working on three cylinders! Does anyone has a clue? What do I have to do? The mechanic who control the exhaust told me to sell it. I would be so happy if it just went back to 120 miles as before. Could it be the converter? What else could it be? Please help, is there anyone out there with a similar problem? Cheers Gauri