We've had our 2008 FX-35 for maybe 10 years now and have always put premium fuel in it. I was thinking about going to regular or mid grade. Is there any risk to the engine? I suspect the ECM will adjust accordingly to the fuel and if anything we may notice a slight reduction in performance. Who is doing this and how is it working out? We live at 2200 feet, the car has just over 50K miles on it and our local fuel octane is 87, 89 and 91. Thoughts?

Hello,

The last time I took my FX35 in for smog, the tester advised me to run the premium fuel, which I had not been doing although I understood it added about 25 hp. He said that with the premium fuel and the more power you get better gas milage and less strain on the engine. My understanding is this is not true on all cars but for the cars that the manufacturer lists as getting significantly more HP on premium but you can also run on regular. I tried this on my other car, Mazda CX9 2.5 turbo and I did notice the increase in milage and who can argue with more HP? I figure that with the money I save in gas milage it almost works out even with the higher gas price of premium.

My FX has 260,000 miles on it and no major repairs as of yet.

Thanks for the reply. We have decided to keep running premium.