What octane gas do you use?

[jdstrickland]

Using Regular in an engine that prefers Premium is a false economy. Modern engines will detune themselves if the fuel grade is too low and results in engine knock/ping. Knock is bad for an engine, so if it is detected then the computer will retard timing to prevent knock from happening. The result of detuning is reduced performance that most drives will not feel in the seat of their pants.

You should keep a log for a while of using Regular gas, and then repeat the log using Premium. You want to calculate the COST PER MILE, you do this by dividing the MPG into the price per gallon.

Lets say that using Regular, gas costs $3.50 and you get 20 mpg, the cost per mile is 17 cents, 17.5 to be precise. Now lets say that on the tanks of Premium you get 23 mpg, and the price per gallon is 3.70, the cost per mile falls to 16.1 cents. Premium costs less to use than regular because it is more efficient, greater than the difference in price.

I pulled numbers out of my ass to illustrate the point, your numbers will be different but the point is still valid and you need to know what the numbers are before you can jump to the conclusion that lower price fuel costs less to use. You might be surprised to learn that the higher cost to fill the tank pays for itself.

Cost per mile is what you want to know, not miles per gallon.

[JCL]

Originally Posted by jdstrickland

Using Regular in an engine that prefers Premium is a false economy.

It isn't just about the cost. By keeping detailed mileage logs, for every tank, you can determine your efficiency, in my case in litres per 100 km. With my X5, he best mileage was on 89. That is a pretty good indication that for my driving, and my local fuel, the computer was not retarding the timing.

Saving money was a bonus, but wasn't the reason to use 89 in my case.

If there was in fact a 3 mpg difference, in my case, I would have used the premium, simply to get the performance out of the engine that it was designed to deliver. Conversely, if 89 delivered that design performance, then putting in premium would be a waste.

[JCL]

In a search for more of your gasoline dollars, the oil companies started upselling the benefits of premium gasoline over 60 years ago. Claims like more power, cleaner burning, and 'treat your car right'. This one even claimed that buying premium was an alternative choice to buying a new car.

[TiAgX5]

Ricky got it all wrong when he heard his car would run better with Ethyl in it.....

[motordavid]

+ w/a few of the above...
I have run regular, 'mid grade', and premo of dozens of brands in our '01 3.0, over the past 14 yrs.

Have never had a 'bad tank' regardless of octane or brand, and the mpg has not wiggled much over 105k miles and those 14yrs of the usual stop & go, climbing our mountain road several times per week, lots of trips, etc.

I don't shop for gas, eg driving around to save 20 Cts, nor do I run non-premo to to save any dough: I just buy gas when/where I need it, and pump what 'grade' I feel like using...

Other than an exhaust cam sensor replaced, (code 172, sub menu 12), and a new fuel filter installed for reasonable maintenance at ~ 100k miles, I have not had a 'fuel' hiccup in all these years, running what I feel like running, gasoline-wise.

Anecdotal, and one can pump 91 or 93 every tank, if it makes one feel better about the situ.

By the bye, I had been looking forward to the 'What gas should I/do you use' thread, that comes up on the Jukebox about 3 times per year here, over the past decade.
GL, mD

[Bmwtvboy]

I usually run highest oct. But for a short time I tried 89 and noticed poor mpg and lackluster acceleration. After 200 K miles and regular syn oil changes it runs smooth and fast when I need it to.

[Ricky Bobby]

I love mD's anecotes because I'm sure hes seen the same threads so many times over the years.

I've been putting 93 octane in cars that require 91+ since I turned 17 and started driving a VR6 Jetta. I've heard the adage a million times from people who do nothing but pump regular on their new Bimmer leases and scoff at how much "more I'm spending" on gas vs them, while their Grande Mochalattefrappucino#lovewins blah blah costs them $6.50.

Run good gas, don't run on fumes. Use Techron if you want, maybe some Lucas if you like using lubricating additives. I have a Shell 2 miles from my house so I fill up at their station, most other times its Sunoco or BP. I won't put regular in my X because I like to follow the recommendations of the manufacturer, and with less octane on our cars comes slightly less mpg and performance.

If I didn't have 93 available I would run 91 if that was the only premium offered. I stay away from non-brand stations that most frequently come up on the news for having extremely cheap gas and water in their tanks.

[bcredliner]

Don't have a clue as to validity but interesting reading.

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