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Chubby Cheddar on Today: There is no reason to use High Octane gasoline

Hmmm...For those of you who don't know Csaba Csere (somehow pronounced something like "Chubby Cheddar") said on the Today show 'there is no reason to use high octane gasoline."

I dunno, but in my small, 4 cylinder engines I tend to get 4-6 MPG more than using even mid-grade. I won't put anything lower than mid grade in any car I own. For some reason, however, my '89 Mazda 626 and the '88 Supra seem to do better on 89 Ocatane, and all the others do better on 91.

I did a spreadsheet once based on fuel economy from a 95 Tercel I had, and using mid-grade I was getting about 38 MPG, while on Premium I was getting

43-44!

I calculated the price per gallon at the then current rate of $2.58 for premium and $2.48 for mid-grade, came up with gallons per mile and extrapolated that I actually SAVED $265 over the two years I owned the car by using Premium.

With my 1985 Corolla GTS, I was getting ~32 MPG with mid grade and 36 MPG with Premium.

However, the Mazda does worse on Premium, it goes up about 2 MPG when I use mid-grade. The Supra seems to like ~91 Octane, so I mix the fuel in the tank on alternate fill ups.

The Scion is a real experiment. It gets ~27 MPG on mid grade and 32-33 on Premium.

Hmmm...NO reason to use premium? Add to that that I have NO fuel related problems...

Reply to
Hachiroku $B%O%A%m%/(B
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Plenty of reason for high octane on smaller high compression / high performance engines. For a big old average tune V8, hell no, they are happy with most anything resembling gas.

Reply to
Pete C.

How much ethanol is in the various grades?

In Ontario it varies.

10 percent ethanol in regular to zero percent in some premium.

Using your figures of around a 10 percent increase in miles per gallon on premium and our gas prices, the math doesn't work me and my vehicle,

.$0.24318 per mile on premium.

$0.24027 per mile on regular.

Maybe I will try premium and see if there is an increase that justiifies the higher cost.

Reply to
G

More years ago than I'd like to remember I had a Ford with a HP 335 horse

390 engine - that damned thing would only run on Chevron Custom Supreme any other premium it just didn't like.

I'll catch some shit for this, 86, but my guess is the older cars have probably just enough cylinder head deposits to increase the compression, MAYBE giving you better mileage on higher octane. FWIW, my Highlander says to use 87 UNLESS I need higher performance such as towing a trailer in the hilly country,.,.

Reply to
ron

My Ranger is spec'd in the manual for 87 octane, but on hot summer days it'll ping under almost any load unless I put in premium. I've never done a fuel mileage comparison between the two (I only use premium to stop the detonation), but a number of years ago on 87 I figured it out to be averaging just shy of 30mpg, which is apparently about 5-6mpg more than average for a Ranger of my configuration.

*shrug*

-J

Reply to
phaeton

Calculate cost per mile to see which is more economical. If the cost is the same or close, go with premium to take advantage of the advanced timing. Note that if you switch back and forth, it takes the computer a tank or two to advance the timing again after it has been retarded on regular.

Reply to
Ray O

What does JSB have to do with the gas I use?

Reply to
Hachiroku $B%O%A%m%/(B

Since the price has gone up, and esp when it was hitting $4 a gallon, I usually do with all cars what I do with the Supra, and that is one fill with 93, and one fill with 89. I keep the tanks relatively full, usually right around 3/4 tank when I refill. I'd rather have gas in case I have no money, and I know at anytime I can just jump in the car and go.

This usually mean 5-6 gallons of whatever, and every once in a while I run the tank down low to get rid of 'old' gas and refill with fresh gas. Since the pumps have credit card readers on them, I don't have to drive the attendants nuts like I used to do years ago...

This method keeps the octane in the tanks at 91~92.

The Mazda is weird. It got below 3/4 tank, and they had run out of Regular, so they were selling 93 at the regular price, so I filled ALL the cars, and the Mazda DROPPED 3 MPG!

Reply to
Hachiroku $B%O%A%m%/(B

But...what about the '05 Scion, with 28,885 miles on it?!?!?!

And my venerable '85 GTS, which I bought 1 year old with 10,020 miles on it (yes, I remember!). It was really the car that started the experiment, with a little black book in the glove to record the results. After about

12 years I figured I had enough 'results', but still calculated the MPG every time I filled up.

And before that there was the '80 Corolla SR5, that did better on 93, and I bought that one with 12 miles on it, and before that there was a '78 Corolla 1200. That ONLY ran (or, to say, I only filled it) with Premium for it's short life (A Mustang did it in at ~55,000 miles.)

Are you ready? That car got FORTY-EIGHT miles per gallon!!!

And ALL figures are OVERALL, town and higway driving!!!

So, here's the run down: 78 1200=48MPG

80 SR5 (1.8L) = 33 MPG 85 GTS (1.6 DOHC) = 36 MPG 95 Tercel = 45 MPG 05 Scion tC = 32 MPG

IIRC after putting Michelin radials on my '74 1200 (FIRST car, and bought NEW!) I think I was getting 38 MPG combined.

Hey, do I get a Nobel Prize for fuel conservation? They seem to be giving them away for nothing recently...

Reply to
Hachiroku $B%O%A%m%/(B

I'll plead the Fifth...

Reply to
Ray O

It is tough to calculate when the fuel is mixed like that although cost per mile shouldn't be too bad.

Reply to
Ray O

It's generally ten cents difference around here, although there is one gas station between UMASS and Smith College where the difference is only 5 cents. Guess what they get filled with there!

Reply to
Hachiroku $B%O%A%m%/(B

Make it Crown Royal and I'll be right over!

Reply to
Hachiroku $B%O%A%m%/(B

Hmmm...I always thought they added ethanol to RAISE the octane?!?!

Perhaps (once) I'm wrong. Anyone know for sure?

BTW, they do this in Vermont also. In Mass., ALL gasoline is required to contain ethanol. Funny thing is, when I would fill the car in Vermont BEFORE they added ethanol was when I got the WORST mileage; 24 MPG with my LHS (it usually got 28 MPG on Mass gas), 23 with a Grand Voyager (it got

27 in Mass), and 27 in my Scion tC!!! (it now gets 32).

Um, we won't talk about the Supra, OK?

Reply to
Hachiroku $B%O%A%m%/(B

I know someone who used to mix Crown Royal with 7-Up. To me, it seemed like putting ketchup on filet mignon

Reply to
Ray O

I think I heard or read one time that lower octane gasoline actually made a bit more btu's/unit, is this true Ray?

Reply to
ron

True, but I usually mix mine with Coke. Makes it last longer, and I'm not that much of an alcoholic! ;)

However, I would like a nice Crown Royal...

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Reply to
Hachiroku $B%O%A%m%/(B

Ethanol waters down the energy content in gasoline.

Gasoline:

1 G1al Gasoline (mid grade) = 125,000 Btu's

Ethanol:

1 Gal Ethanol = 76,000 Btu's

So E10 would have 76,000btu x 10% = 7,600btu

125,000btu x 90% = 112,500btu

Total btu content 120,100btu or 96.08% energy content of straight gasoline.

E85 = 83,350btu or 66.8% energy content of straight gasoline.

Reply to
G

When regular was 55 cents/gal and higher octanes were 65 cents and 75 cents, it was a HUGE difference.

Today, the difference is still a dime--but a dime out of $2.50. Percentage-wise, the difference is peanuts. Therefore, it pays to do careful cost per mile calculations to see what happens.

Was Csaba talking about new family cars specifically? Because older cars with some miles on them, and some crap in the engines, might do well with, for example, Shell premium--at least for awhile. That was the case for my Lexus. A couple of months of Shell premium cleaned it out, then afterward I used Shell regular--and even though it cost a couple pennies more per gallon, it was much less per mile to operate with.

My dad worries about this stuff--of *course* Acura says "you MUST use higher octane gas!" in my new MDX because their marketing dweebs want you to think you bought a "premium" car. But in this case, Csaba is right: use the 87 octane, and you're fine.

Now, if you want to do the cost per mile calculations, that's up to you. But engine damage? Not on your life. Honda isn't that stupid, and neither is any other manufacturer.

Reply to
Elmo P. Shagnasty

The BTU content of regular and higher octane fuel is the same if the only difference were octane content. Premium fuels usually have other additives besides octane, which muddies the comparison somewhat.

Higher octane fuel allows ignition timing to be advanced more and compression to be higher, both of which allow the engine to burn the fuel more efficiently and increase performance.

Reply to
Ray O

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