Regular gas in the Mazda 3

[wolf_06]

Gooday folks,

I recently posted about fuel economy with regular vs premium gas.

This week so far I managed to put 350 km on half a tank of gas, I filled up at a Exxon Mobil gas station with regular 87 octane 10% ethanol.

Still have 300 km ish to go.

I drove mostly highway, a few stops here and there, 110 km/h, some hills, a bit of stop and go, minus 6 degrees outside, slushy roads, floored it 2 times to pass some turtles,

Overall, I am impressed with this 2.0L Skyactive.

On top of that, with the Mobil gas station, I collect points to buy more gas or stuff at the supermarket, its great since I do high mileage.

Is premium 91 octane really better in this case? how bad is 10% ethanol? does it rust the internals?

 

[PimTac]

Rust the internals? I don't get that one.

If it runs fine on regular then go with it.

 

[UG_Passat]

I don't believe 91 is required for your car. Just stick to 87 and save your money

 

[Lolvoguy]

Dunno about your Mazda, but my old BMW in the sig below does not take well to Ethanol (in most regular/mid grade gas in Canada).
As soon as I ran my first tank of prem. 94 Octane Chevron fuel, it ran like a much newer (and smoother) car. This was illustrated with less cranking time to start, smoother idle, acceleration etc.

IIRC Chevron 94 has been known to be Ethanol free.

IMHO, most newer vehicles (yours included) run just fine on regular.
No need to upgrade/pay extra for the fancy stuff.

 

[DGXR]

Sounds like you are doing great on regular. For a modest price, it might satisfy your curiosity to try a few tanks of premium and track the mileage. Do more than one tank, and do them back-to-back. And please post your results if you do this.

 

[wolf_06]

Originally Posted by DGXR
Sounds like you are doing great on regular. For a modest price, it might satisfy your curiosity to try a few tanks of premium and track the mileage. Do more than one tank, and do them back-to-back. And please post your results if you do this.


I used premium before mostly, and now used a few fill up of regular, top tier brand like Mobil, cant seem to find any difference...

 

[UG_Passat]

Originally Posted by PimTac
Rust the internals? I don't get that one.

If it runs fine on regular then go with it.


Ethanol is very hydroscopic, so the worry is the water it attracts can cause corrosion in the fuel system

 

[ammolab]

A local station has regular for $2.03 a gallon and Premium?

$3.42 a gallon! Just waiting for some guy who drinks imported beer, bottled water, and puts premium in his truck, because it its gotta be "better", to fill up without looking at the price.

 

[VQ35DE]

I use 93 in my Skyactiv.

 

[Eddie]

I tried several tank full of 93 in my 2.5L Skyactiv and there was no difference in fuel consumption or performance over 87. The Skyactiv engines, 2.0 & 2.5L are designed to run on 87 in the USA. ed

 

[Rand]

I have been using 88 octane (e15) its currently 1.62/gal best price for 87(e10)is 1.82

I dont notice much difference between 93 and 87/88 except in midsummer towing.

I can change to sport mode with 87/88.. and its more responsive than 93 in auto mode (except when flooring it)

right now some stations here are
1.57 for e85(51-83% ethanol usually lower% in winter for vaporization)
1.62 88octane up to 15% ethanol
1.82-1.99 87octane up to 10% ethanol
2.12-2.59 89 octane upto 10% ethanol
2.42-2.92 92/93 octane upto 10% ethanol.

The price spread is C R A Z Y with a capital C.

88 octane is the real winner.. as its 87 mixed with a small amount of e85 at the pump (under 10%)
yet is 20cents cheaper than 87 octane.

Fuel economy is similar on 87 and 88.

FWIW: I tested some 87 and 88 octane last year and the ethanol percentages were 7% for 87 and 12% for 88
this wasnt a laboratory grade test though.. simple water test with graduated cylinder.
Since that was mid summer I'd expect the 88 to have even less ethanol now(closer to 10%)

Disclaimer: This is how it was explained to me by a friend who manages a station that sells the e85 and e15

 

[Kestas]

Ethanol is a problem if it is stored in the fuel system and the vehicle sits unused.

Premium now costs 38% more than regular where I fill up.

 

[wemay]

Both Turbo'd vehicles in my signature recommend 87 octane. I had been using 93 in the Santa Fe until my wife told me she's been using 87. She also filled the VW with 87 the one time she drove it. Neither vehicle felt or sounded any different and there is no hit in mpg either.

If programmed to run 87, do it and save yourself a few extra bucks. Here, 87 is $2.03 and 93 is $2.95.

 

[JohnG]

88 octane is the real winner.. as its 87 mixed with a small amount of e85 at the pump (under 10%)
yet is 20cents cheaper than 87 octane

Now, I know that SUNOCO had blending pumps many years ago, but I haven't seen one forever. I those cases, they had two grades of gas (and two storage tanks) the pump would (hopefully) mix the two by ratio. Of course the amount left in the delivery hose was disregarded, so my Harley would suffer from time to time.

 

[Ws6]

Originally Posted by Eddie
I tried several tank full of 93 in my 2.5L Skyactiv and there was no difference in fuel consumption or performance over 87. The Skyactiv engines, 2.0 & 2.5L are designed to run on 87 in the USA. ed

This was my experience as well, although my 2.5 turbo skyactiv does benefit my 2.5 n/a skyactiv showed zero benefit.

 

[Ws6]

Originally Posted by Kestas
Ethanol is a problem if it is stored in the fuel system and the vehicle sits unused.

Premium now costs 38% more than regular where I fill up.

87 with ethanol is $2.09/gallon in my area, on average. 91 with 0 ethanol is $2.59. Same station, Top Tier. 25% difference. Horsepower difference in my vehicle is around 10%. I'll take it.

 

[Olas]

better MPG with more octane, and better performance with more octane.

 

[Rolla07]

No point using 91 unless it says to in manual. The price difference in Canada is crazy... the other day it was 20 cents a liter...most cars use 87...if it caused any rust to the internals we'd of known by now.

 

[BMWTurboDzl]

Originally Posted by UG_Passat
Originally Posted by PimTac
Rust the internals? I don't get that one.

If it runs fine on regular then go with it.


Ethanol is very hydroscopic, so the worry is the water it attracts can cause corrosion in the fuel system


The problem is when ethanol falls "out of phase". Basically it settles on the bottom of the tank. If the tank were metal and the fuel sat that long enough it would cause rust.

DOE's National Renewable Energy Laboratory (NREL) conducted a study on this and per their results it takes a min of 3 months in a high humidity environment for before ethanol absorbs enough water to fall out of phase which btw is well AFTER the time it takes gasoline to go stale.

So moral of the story is that corrosion of fuel systems is a non-event for any vehicle made within the last decade probably two decades.

 

[Olas]

Originally Posted by Rolla07
No point using 91 unless it says to in manual. The price difference in Canada is crazy... the other day it was 20 cents a liter...most cars use 87...if it caused any rust to the internals we'd of known by now.


All cars made in the last 20 years have computer controlled timing and knock sensors, so there is ALWAYS benefit to using higher octane levels.