I cut and pasted this from a Popular Mechanics message board. I thought it was appealing because I did think about this myself. I was curious what people's opinions are about it. I apologize ahead of time if this has been talked about but I haven't come across it yet. Thanks all .

Popluar Mechanic's answer to this question is "yes" . The other thing I do know is that the halfway point on the gauge does not necessarily reflect a half tank. I would imagine half would be somewhere between half and three fourths so I think some adjustment is necessary.

 

The post on the PM board sounds like a case of penny-wise, pound foolish. Here there's a difference of 10¢ between mid grade and super so an 11 gallon fill-up will save 55¢. When looking at the cost of something I factor in my time, so to do this I'd have to watch the pump, stop it at the appropriate time, run my card through again, and continue filling. Not worth it. The same poster probably takes his newly filled car and extra $1.50 (let's say he's driving an SUV) to Starbucks to buy a $4 cup of coffee. My point is there are better ways to save money.

To keep my gas costs in line I look for lower priced quality gas (Hess is usually cheaper by me) or fill up at Shell on the days they offer 6¢ off per gallon of premium. I also pay with the Discover "Platinum Gas Card" which gives 5% cashback bonus on gas purchases. I then use the bonus money towards my card bill. This way I save money without any effort on my part.

Oh, and I drive a MINI on a daily basis

Paul

 

Is the higher octane needed in the regular Mini or is it just for the "S" model?
I can only get 91 octane here in Colorado.

I believe there is a 2 gallon reserve in the Mini's which may be reflected on the gas gauge.

Our mini is on order, don't have it yet. :(

 

I"m curious why the MCS needs the higher octane when it has a considerably lower compression ratio then the MC. I am going to suggest that 8:1 is still high enough to require it and that there is more to the octane requirements then just compression ratio. It makes me wonder what the compression ratio on vehicles that only need 87 octane is. I know you can always put in a higher octane but it is not recommended to use a lower octane in an engine that needs it. I had a 1972 Datsun with a 1600 cc engine that only needed regular but ran and got considerbly better mileage on premium. I would not be penny pinching like this character did. I would just use the 93 octane which in my area does not exist, only 92 unless you go to the airport and fillup. I like the smell a aviation gas.

 

Compressing air as you shove it into an engine effectively increases your compression ratio. While at standstill it's 8:1, it's considerably higher as you're forcing air into the engine with the supercharger.

 

I used to live just outside of Denver. Your octane requirements are lowered at higher altitudes. That's why you'll see 85/87/91 in CO instead of 87/89/93.

Here's a good explanation of octane. Altitude is discussed in the 2nd to last paragraph.

If you still feel you need more octane just add rice to your fuel

Paul

 

There you go, that makes sense.

 

You can average it out and save even more by going to mix of 93 and 87. For the money, however, it just isn't worth it to me.

 

Correct! Why do you think us t/c'ed cars love the race fuel? Because crappy 91 octane knocks and causes the ECU to retard timing based upon perceived knock levels. To get that advance timing back you need to do something to quiet the knocks. Higher octane is on way to help keep the ECU happy with lower knock readings.

 

Try rebuilding your blown engine caused by knock/ping/detonation. That cost is much much higher than using higher octane fuels. Of course a stock MCS, in most cases should be fine on 91. It's when you start pushing the envelope with higher boost levels that you should become concerned. Can a stock MCS run better on higher octane? I think I overheard someone with a stock MCS that was able to get more advanced timing due to lower knock readings when using higher octane fuel.