interesting - no mention in your manual that using lower octane may result in detonation?

 

Yes there is. Here, read this carefully, it is interesting:

"Minimum fuel grade
Do not fill up with fuel below the speci‐
fied minimum quality; otherwise, the engine
may not run properly.◀
If you use gasoline with this minimum AKI rat‐
ing, the engine may produce knocking sounds
when starting at high outside temperatures.
This has no effect on the engine life.
Minimum fuel grade
The use of poor-quality fuels may result in
harmful engine deposits or damage. Addition‐
ally, problems relating to drivability, starting
and stalling, especially under certain environ‐
mental conditions such as high ambient tem‐
perature and high altitude, may occur.
If drivability problems are encountered, we rec‐
ommend switching to a high quality gasoline
brand and a higher octane grade — AKI num‐
ber — for a few tank fills. To avoid harmful en‐
gine deposits, it is highly recommended to pur‐
chase gasoline from BP or Top Tier retailers.
Failure to comply with these recommendations
may result in the need for unscheduled mainte‐
nance.◀"

 

got it, thanks. i don't nearly drive the car enough to have refilled yet - last fillup was 11/21/14

 

While pondering the use of lesser grade fuel than recommended you should consider at what elevation you drive and type of MINI set up you have....At sea level more critical to use a higher rating than when in the mountains due to air density. And if you drive a force inducted engine (turbo/supercharged) at sea level or near that, then the higher the better for max hp.

And keep in mind, those anti knock ratings you see on the pumps are not always an absolute or accurate as to what's going into your tank at the time of purchase. Those numbers can vary depending on the batch, so you may think your pumping 87 and it could easily be 86 or lower.....

 

Unless the gas supplier is willing to pay a huge fine, the gas in the ground (or in an above ground) tanks, will NEVER be of lower octane. As I stated earlier, I used to be the manager of an oil storage facility for a mid major oil company. Every bulk deliver of fuel is sampled and analyzed before being put into storage, and the entire tank is analyzed prior to being released for use. They are always a few basis points higher than required. Regular is usually 87.2-3, premium is 93.2-3 (93 is in the MD, PA, and VA area) I'm talking about MILLIONS of gallons here.. (we had 2 93,000 barrel tanks for reg gas. a barrel is 42 US gallons. that's 3.68 million gallons each...)


Also be aware that there is no actual mid grade gas. It is a blend of premium and regular, and the resulting blend is a minimum of 89.2-3 octane.


There are mistakes when delivering gas to a station, but, it's always caught,, and corrected. If a tanker driver puts the wrong grade in a tank, (they aren't usually the brightest bulbs...), the result is evaluated. If Premium is put into any other tank, it stays there, and you get bonus octane. If reg, or plus is put into premium, the entire tank is downgraded, and pumped into the correct tank, and a new tankfull of the correct grade is delivered.


All that costs a lot of money, so it tends to be very rare. But EVERYONE takes it seriously...


So again. if the pump says it 87 or 89 or 91 or 93, or 94... It's NEVER, ever, less than that... It's usually more...

 

I never deal in absolutes as there is no such thing as "never." Seems you were a good store owner, and congratulate you for that and thank you. But, that is not the case for up to some 5%+ of the gas store owners in each state. ( That is the average )


The Department of Weights and Measures and each states Field Inspectors are responsible for these tests. There are 9 inspectors for the entire state of Massachusetts.....Each station may not be inspected more than once a year. That leaves a lot of room for error I am not willing to take with my MINI.


In this report from Car and Driver Magazine "Of 2816 samples from stations that were processed in 2005, 217 failed, the majority because of a low octane rating."


And in this CH11 Report from Dallas TX From story: "During a follow-up inspection the following week, the mid-grade 89 at the Denton station only measured up to 87.7 octane — and the premium 93 octane only tested at 92.1.
The station adjusted the pump labels to accurately reflect what was really in the pump — so it could continue selling the gas. The manager declined comment.
Last year, 13 percent of octane samples statewide failed to match the tag on the pump. The department of agriculture issued 46 violations. Aside from the state tests, consumers really have no real way of knowing what’s in the fuel."

 

I was not a store owner. I was management of an oil storage and deliver to station terminal..


If that actually happened, then it was the store owner that did it. The gas we put into trucks for delivery to stations was right. The gas our drivers delivered to stations was always right or made right.


(I can't vouch for independent trucking companies and shady owners of non branded stations.) but the top tier gas we delivered was right.

 

My Justa is driven in a moderate climate at 2,300 feet in altitude that only sees a few days of 30 degree weather a year but months of 100 degrees plus. What I have found works well for my engine is the 91 octane year around with Lucas Octane booster during the hottest months only. As the hottest days are the only ones I run through the 8,000 foot elevation mountain roads, the octane booster seems to help there too. Your results may vary, I drive the car fairly hard.

 

OP Here. Been running the past few tanks on 89 with no discernible issue. No knock or otherwise that I've been able to detect, which is what I expected. However, I do believe I've seen a decrease in overall MPG while on 89. Not sure if it's from the particularly cold or what, but I'll go back to 93 and see how the car does back on it.