This may sound cheap, but often when I fill up, I will put in 8 gallons of 93 octane fuel and then top it off with about 8 gallons of 89 octane fuel.

The logic here is that (89+93) / 2 = 91, which is the octane requirement for the G. I am in Dallas and there is no 91 available, just 87, 89, and 93.

Fuel grades are typically 15 cents more than the next, so they may be priced 2.65, 2.80, and 2.95, respectively.

Using this method (at the above prices) I save $1.20. Okay, woopee - barely worth the effort. But if I'm in no hurry, I am happy to make $1.20 for 1 minute of effort (that's $72 per hour).

But my question is -- will normal driving allow the two fuel types to mix adequately to actually create a 91 octane fuel? Or am I essentially burning 1/2 a tank of 93 and then 1/2 a tank of 89?

I have heard fuel tanks contain chambers or walls with holes which help prevent fuel sloshing and add rigidity, but that may hamper mixing while driving. Can anyone shed any light on the interior structure of an automotive fuel tank?

 

I think you should be fine but just put in a bit more 93 to be on the safe side. Here we have 87, 89 and 91. What I've heard is that the pump mixes 87 and 91 to get you 89. I think once you start driving it should blend, so maybe put in 93 first?

 

op,

i think you'll alright. i've heard about people doing that before, but it's such a hassle. props for you! despite, the different levels of octane simply are different because of the different concentrations of octane. in short, because both are non-polar, they should mix readily.

...you'll be alright.

 

That's a lot of trouble to go through to save a couple of dollars per fill up only to end up with 90 octane gas. But yes, as was mentioned they do mix and "split the difference" to make 90 octane if you mix them in equal parts. More power to you if it works for you.

 

to ensure proper mix of the fuel you will need to do doughnuts on your driveway...

 

In one month you can save enough for a couple of loafs of bread and a can of SPAM.

 

No! I did that with my G8, got horrible pinging, and then was mocked incessantly by the board members after I asked the same question. Lol.

 

i thought mixing low quality with high quality gas was a bad idea? Just cough up the extra 5-7 dollars for a tank of premium dude. That's just cheap living. what you doing with a G37 then?

 

Be careful.....93 and 89 are like oil and water
They mix while you are driving but they seperate out once you park overnight .
Might as well run your car on Italian dressing....

 

Consider yourself lucky with those prices..... up in NY 93 Oct is currently $3.16/gal, the cheap stuff is $2.95....

 

IMHO: A better way to is alternate tankful between the two 89 and 93 but use same manufacturer, I prefer Chevron. This way you will not only save $$ but car performance won't be noticed/impacted.

I have done this on my 03 G35 coupe, since 2002, with no impact and I have over 110K miles/22mpg.

 

That's a lot of effort to save a couple of bucks at each fill up.

 

Saving couple dollars like this I think it is worthless. It's like 100 times you fill it up, you will save 100 dollars, but think about all the effort and time you are spending.
I would rather change my driving style lil bit, and not accelerate fast all the time, and cruise highway at constant speed. (heard 55~65 is most economical speed for mpg)
That will save you more in a long run.
Put premium gas and know that its PREMIUM. Satisfaction of having it, using it, I think it's worth more.

 

your saying every 2nd time u fill up with 89 your CRAZY thats stupid

 

Some of you say that, but I really don't see it.

Swipe card, key in number, stick the hose in tank. I said it takes a minute, that was exaggerating!

Maybe those that laugh have never had to pay for a family of five on one blue collar income. Or maybe they have money to burn, or daddy's credit card? My kids are grown & gone and I make a lot more money today.... but it's really no trouble to do this. I try to save a buck where I can. Hell, my back is sore because I've been painting my friggin' 18x10x10 bathroom all night. I could pay someone, but...

Don't get me wrong, I greatly appreciate everyone's comments.

One poster said there was a chance the fuels seperate when the car sits still - is this true? If so, I won't mix fuels again.