My turbo Mazda says it needs 91 octane. Can I pump 1/2 tank 89 and 1/2 of 93?

Question

When 87 octane is $3.15, 89 is $3.25, and 93 is $3.45, why does 91 cost $3.42, not $3.35? Why is the jump so high? Is there a good reason, or are the oil companies just sucking us dry?

Answer 1

Yes, of course we're being sucked dry...but our governments assure us that there is no price fixing so it must be so...right?

Higher grade/higher octane gas also contain more additives like fuel systems cleaners, etc, so that's where some of the cost difference comes from.

As for the mixing, don't bother. If you actually calculate the difference in price it's not very much. If you have a fairly common 15 gallon tank a fill @ $3.15= $47.25 where a fill @ $3.45 = $51.75, a difference of $4.50. If you try the 50/50 split you'll only save about $2.25 per tank. Is it worth the effort?

Answer 2

Wendy,
The answer is yes you can mix. In fact most modern gasoline pumps do just that. They have two tanks storing fuel for the gas station, the lower octane, and the high octane. The midgrade is just a mix of both. Some stations have multiple grades of fuel, IE Sunoco No the pump it is not just a simple thing, it is metered and is what it says it is Octane wise. But you can do the same thing. Simple way to figure what octane you really have is multiply the 87 octane by number of gallons pumped, add that to 93 x number of gallons. Divide the total number by number of gallons pumped. IE 87x5=435 93x5=465
435 + 465 = 900 900/10 = 90 octane.

To get 91 octane if you pump 10 gal total of fuel you would have to pump in 3.5 gal of 87 and 6.5 gal of 93 octane. which gives you 90.9 octane.


I own a Maita Mazda Speed, It is factory turbo charged. 91 is the minimum fuel required., because that is the highest offered in some states. The car will run on it, but due to the computer and sensors, it will run better with higher octane fuel. Better fuel mileage, and power. Unless you own a Mazda made before the early 90's the computer will sense the lower octane and make adjustments to timing and amount of fuel used, to protect the engine from damage.

As to why the gasoline prices vary. Free enterprise. You can shop where ever you wish for gasoline, look around and buy else where.

When I was 18, gasoline was .35 cents a gallon. But I only made 1.80 an hour or 20% of what I was paid to work one hour. Now a gallon of 93 octane gas is 6% of what I make an hour. So I find it cheaper now. But I have paid my dues, went to college, work in an industry that I like, and can pay well if you do good work. Or you can complain about how unfair the government and big business is.

Answer 3

Up until a few years ago, more oil was being discovered than was being consumed. Now more is being consumed than is being discovered, therefore, it is only going to get worse. Yes we are being ripped off. Only solution I see is driving economy cars or the new gas/electric combos. Are the middle eastern countries likely to lower oil prices because they like us so much?

Give it a try with the mixing. In the winter months you might get away with the 89 octane. Some of the turbo Mazdas had knock sensors that retarded timing if the engine started to knock from bad fuel or too much boost. Not likely to have problem if you don't get into the turbo too often. The turbo had lower compression ratios than the regular motors so, in theory, you should be able to use a lower octane if the turbo is not in use.

Answer 4

Yes, the truth is, they're sucking our wallets completely dry. But as for your Mazda needing high octane, don't screw around too much with that. It's there for a reason. If it's an old boosted Mazda, go premium ONLY. Older computer systems in cars can't compensate and re-tune well. A newer car its not so critical, the ECUs can retard timing and adjust fuel curves. But I still don't recommend it. Turbocharged cars are very sensitive to fuel quality. I drive an old Merkur XR4Ti, two actually, and only run 93, 94 if it's there. And don't cheap out at Speedy Q, Marathon, Speedway, etc. Go with Shell, Mobil 1, BP/Amaco, Texaco. Take care of that Mazda! You paid money for it I'm sure so nurture your investment.

Running low quality fuel can cause detonation, you can fry your rings and pistons. Also temperatures can climb and other problems can arise. Plus bad fuel gumming injectors and etc.

Answer 5

gas stations have 2 tanks, one for 87 octane and one for ninety one octane (this would determination in case you stay in severe altitude states which have 80 5 octane). on the pump you opt for the grade of gas by urgent a button. in case you chosen the 89 octane, the pump mixes gas from both tanks. i desire you do not recommend "the position do you turn it" on your vehicle. The more moderen vehicles have pcs that administration the air/gas mix and make amends for the changes. you simplycontinual. even if, in the journey that your vehicle knocks once you step on the gas, you should apply a larger octane grade as it is risky for the engine.

Answer 6

Yes they are inflating the prices but there is definately a difference in the fuels. You should have thought about that before you bought a car that requires a higher grade fuel.