I cannot find any info on this in the forum so I'm posting a new question. I know Mazda recommends using Regular fuel in the CX-5 but I'm getting crappy mileage in town, roughly 19.5 mpg.
I thought I'd try Premium but made no difference but now it runs like a race car.
So I've got 2 questions:
1 Am I doing any harm to the engine running Premium?
2 If I add something like a K&N air filter will that improve things like mileage?
Thanks, Mike

 

Adding a K&N will do exactly nothing for fuel economy. Running Premium fuel will not provide you with any extra performance, and technically should net you slightly less fuel economy as a gallon of Premium has slightly less caloric content than a gallon of Regular.

 

My seat of the pants impression of upgrading to premium is just as you describe: runs like a race care (from my experience in a different vehicle). I suspect the engine management system is fully capable of taking advantage of higher octane fuel and that's what I plan to use when I take delivery at the end of the month.

 

LOLz, Mazda says otherwise.

 

Well I see the rating for my local regular is 91 RON which is what the manual calls for so I guess best to stick with that

 

I haven't yet purchased my 2019 GT Reserve (turbo engine) but when I do after about 10,000 miles I'll try a 50/50 tank of 91 octane and 100 octane fuel to see if there is any difference. I have an accelerometer and will test at the same altitude and temperature to keep variables to a minimum. I'm betting I'll get nearly 97 octane with this mix.

I'm selling my gutless 2013 Prius v wagon to a relative B/C I can no longer tolerate it and its CVT transmission. Besides, we just installed solar panels on our house so I've done my part for the environment. I don't see BMW, Audi, Merceds or Lexus compact SUV drivers losing any sleep over their lower mileage. (But wait - they are entitled. I forgot.)

 

I have to say, a waste of effort, the higher the altitude, the lower the benefit of higher AKI fuels.

 

Just recalling a conversation with a former oil company employee telling me that it really does not matter (other than spending more money) if you use regular or premium. FWIW, I have been using regular since day one in our CX-5 (regular recommended anyway) and cannot justify the extra cost for premium.

 

Shipo,
Yep, I'm aware that higher octane is virtually unnecessary at high altitudes in non-turbo or non supercharged engines as the air pressure/02 content is too low.
But, with forced induction engines higher octane is still a good idea B/C there is enough air pressure/02 coming in.

But I'm at 2,000 to 3,000 ft. altitude here in the Las Vegas valley and high octane gas is a great help in this engine.

Eric B.

 

Au contraire, mon frère. With a high compression naturally aspirated engine or a forced induction engine (supercharged or turbocharged) which is, by definition, high compression, higher octane gas will give more power. That oil company employee must have been speaking of "normal compression" engines where, true. it would be wasted money.

When I owned the last generation twin turbo RX-7 I found a great increase in power using costly 100n octane fuel. And how I loved the unique aroma of that potion!
They should make a man's cologne out of it.

Eric B.