Question Guarantee and conversion LPG LPG LPG

Hello wanted to change to Subaru for the next car due to the comprehensive warranty. Unfortunately there is not the XV with diesel and automatic. Since I drive 40000 km in the year I would have had the petroler converted to Lpg at the Subaru dealer. This told me the guarantee expires but if I do all repairs with him and no other dealer, then this would not be noticeable and the garntie will be preserved. What should one think about it?