I drive the g37x, my dad has an m37x (2012).

Thoughts about gas octane? He's using regular, I put in premium.

Anyone have suggestions on what is necessary for the M? Obviously the manual says premium only, but not sure if that's just a suggestion.

Thanks in advance!

It's not a suggestion. The VQ37 is designed for premium gasoline. Running regular hurts fuel efficiency of the motor. Robs of it a ton of power (at least 20HP). Motor sounds terrible (it's doing more work to combust the fuel). And isn't very good for the longevity of the motor.

Most importantly, by hurting your fuel efficiency, the regular gasoline is actually costing you more. The $4 you save (about a gallon worth of gas/roughly 20-23 miles of driving) is offset by the lower MPG you will achieve using regular. I've witnessed this first hand with many cars, old and new, and it's always the same result. During Hurricane Sandy in NYC, we had no choice but to fill up 87 once until I could get 93. In my 2012 Audi A6 3.0T it completely ruined my MPG. Normally a tank provided about 300 miles before the gas light came on...but with 87 it was 250 miles and dog slow performance on top of that. That's 50 miles, about 2 1/2 gallons worth I'd normally get with premium.

2 1/2 premium gallons = $10. The $4 we 'saved' involuntarily filling up 87 cost us 50 miles in driving range. The end result being a $6 loss ultimately.

I've experienced this with numerous cars: FX35, Volvo S60 T5, Audi A6 3.0T, Benz E350, Lexus LS460, Toyota Tundra 4.6L, etc.

Thanks for the detailed reply. I'll set my dad straight!

"Silent pinging" will damage engines ...

When the engine electronics are trying to compensate for reduced octane, that is what happens to avoid what used to happen in older cars: "knock".

If a car manufacturer says "Premium", stick to premium. If the car manufacturer says "Regular", then you can use Regular ... at that point, using Premium is not going to help enough to matter.

Finally, remember that, for most people and the amount they drive, the difference per month between regular premium is about $15 to $30. Why take a risk?

Frankly (and this is NOT meant to be pejorative really), if that amount of money per month is a problem, then buying a luxury or semi-luxury car is the wrong thing to do financially anyway. Consider selling and getting a less expensive car, that will be lower to run and maintain.

Z

Do not go below 90 Octane.

I use 89 in both my G37xS and my M37x...no issues and performance and mpg are great. I would not suggest 87 but 89 or better is just fine and I do not believe you'll see much difference by stepping up to full 93.

securityguy wrote:I use 89 in both my G37xS and my M37x...no issues and performance and mpg are great. I would not suggest 87 but 89 or better is just fine and I do not believe you'll see much difference by stepping up to full 93.

You will. I hate to sound crude, but factually you are simply wrong. These motors are designed for premium fuel.