#regular

Duncan writes:

My daily driver is a 2013 Hyundai Genesis 5.0 R-Spec (with about 22,000 miles), making a claimed 429 hp on premium gas (91 octane, I assume). The power dips to 421 hp (claimed) when running on regular. Here in Iowa, we have the luxury of purchasing fuel with no ethanol.

The 87 octane gas w/o corn costs almost as much as 91 with. If it was your money, what would you put in the tank? 87 with no ethanol ($2.40ish a gallon), 87 with ethanol ($2.20ish) or 91 with ethanol ($2.50ish)? Running 87 or 91 without ethanol does improve mileage, whereas I do not notice an increase in performance running 91 or 93 — though it is recommended (but not required) by the good folks at Hyundai.

Steve writes:

Sajeev,

My wife drives a first-generation R50 Mini base model with the dreaded CVT. This is a transmission widely reported (read: complained about on message boards) to not last well beyond 75,000 city miles. Hers is just now clearing 80,000 and it shows no signs of early struggles, even under the hellish torment of stop-and-go traffic in Houston temperatures.

Perhaps coincidentally, my wife has never put premium fuel in this car, despite it being a requirement. Premium fuel would supposedly generate 114 horsepower; without premium fuel, I would guess 7-9% lower, at, say, 105 horsepower. It is a slow car no matter what, but at least it makes up for it in urban maneuverability.

TTAC Commentator sastexan writes:

Sajeev,

I’ve been driving cars requiring premium fuel (91+ octane). When I bought my Contour SVT in 1998, high test was $0.20 more a gallon (just under a 20% premium over regular). But it was regularly always only $0.20 more. In the past decade or so, I noticed the delta going to $0.30 and even more. The correlation did not seem to be to the price (eg, premium did not seem to track a consistent 15% increase). Rather, the difference appears to be a flat rate.

Question for the best and brightest – what in higher octane fuel makes it more expensive?

What inputs are there and how much more does it cost to manufacture?