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Hi guys, I've always been using the Shell V Power Diesel B7 (as per recommendation of German Auto to use Premium Diesel) in my F34 and was happy with the mileage with a full tank as it could go beyond 1k km (a trip from Nonthaburi to Songkhla and I was still having a quarter tank left). However, in the recent months, a full tank goes much less (around 750-800 km) for same trip. I wondered why and I started to test with 600 baht top up to see how long it can last for the past few months. I found out that the car could barely make 230-250km on 600baht now. I always keep my speed less than 80km/h at 1300-1500 rpm so that the car takes less fuel. I keep wondering why the sudden change as I'm following the same service intervals as per recommendation by the dealership. With that being said, I wanted to know what are the differences between the Shell V Power Diesel B7 and the PTT UltraForce Diesel B7. Are there any differences and can I swap to PTT UltraForce Diesel B7? Would it give better mileage? Thanks in advance for your answers/recommendations/help.