Mileage variation with different fuel brands

[Z71]

I noticed something interesting with my 2013 Sonic sedan (1.8 liter engine, 5 speed manual transmission). I get about 36 MPG average with certain brands of gas (mostly city driving with A/C on). I only use 87 octane gas in this car. This engine does not seem to like Chevron gas that much and it delivers about 33 MPG average. However, it loves Shell gas and I get about 36 MPG consistently when using that brand gas. There is no noticeable difference in performance when using these two brands of gas.

At first I thought it was just a coincidence. But then I tried several times to run the car on Chevron and Shell gas from different gas stations and results were pretty consistent.

 

[Papasonic]

Could one fuel contain ethanol, and the other not?

 

[KlassKlown]

wonder how "V-power" will do for ya

 

[Z71]

All fuels around here contain 10% ethanol.

 

[busterbrown]

All fuels around here contain 10% ethanol.

Same here in the Detroit area. About a year ago, there was one station in a suburb that was listed on buy -real-gas-com. Claimed it had ethanol free Premium. When I got there, all grades were ethanol blended.

 

[lousypirate]

Usually it has to do with how much water is in the fuel.

Try premium, you might go over 40.

 

[Z71]

Usually it has to do with how much water is in the fuel.

Try premium, you might go over 40.

I just might do that. I think the performance will certainly increase because ignition timing will be able to advance more. And this also translates to slightly better fuel economy.

 

[Hdmanny]

I tried a higher grade and it was not worth the cost. If the car is designed to use 87, a higher grade will not make it run better. Higher octane is just to prevent detonation in high compressiion engines.

 

[Swordsmith]

I tried a higher grade and it was not worth the cost. If the car is designed to use 87, a higher grade will not make it run better. Higher octane is just to prevent detonation in high compressiion engines.

This is, by and large, true. However, it does not apply to the 1.4T, precisely because it -was- designed to use higher octane fuel. Instead of an 87 octane car which will run on higher octanes but see nothing for it, it is a 93 octane car (higher really, people have run 106 and seen an upgrade for that as well) which is capable of detecting lower octane and retarding the timing to compensate.

This means performance is certainly better with higher octanes. However, the jury is still out on whether that is "worth it", some have said they see little or no improvement in mpg on higher octane, others, myself included, have seen an improvement there as well; in my case (and some of the others) this turns out to be sufficient to more than offset the added price per gallon; I get more miles per dollar running 93, as well as having a sportier car when I want it.

I have no comment regarding the use of higher octane fuel in the 1.8; I have no experience with that and haven't seen much in the way of numbers from 1.8 owners.

(edit to add) p.s. I note you even have the reason the 1.4t performs better with higher octane correct; the mechanism used to detune for lower octanes is the knock sensor. The car starts with an attempt to run as if it was getting the highest octane fuel, then retards timing each time it detects knock, until the knock stops.

 

[Wydz]

Mine is the opposite, it loves chevron, but hates shell lol

 

[lousypirate]

If you aren't seeing a difference, try changing your driving style

My boss's f150 with the turbo'd v6 almost does a shudder when it starts up, very neat.

My 05 legacy that I had averaged 3 mpg better on premium, and that was an na motor. 3 miles for .30 is worth it every single day of my life.

 

[wbjones]

Mine is the opposite, it loves chevron, but hates shell lol

anyone with enough engineering background to explain the benefits of the nitrogen that Shell touts as the biggie reason their fuel is "better" ?

I use Shell, almost exclusively … but that's as much because of the fuel perks from my grocery shopping (5¢ per gal. for every $50 spent on groceries.. and I'm going to buy groceries regardless of the loyalty card …LOL)

 

[Hdmanny]

I used E85 a couple of times in a flex fuel truck I had, it was 15% cheaper and I lost almost 30% mileage. Will never do that again.

 

[Swordsmith]

I used E85 a couple of times in a flex fuel truck I had, it was 15% cheaper and I lost almost 30% mileage. Will never do that again.

What you're missing is that you also got 20% more power. Normally, the added power is wasted, since you don't drive around WOT anyway. But if you want to turn your Sonic into a little sports car occasionally, a flex fuel setup lets you run a tank of E85, and then go back to normal driving filling up with 93.

For a truck, I would think it would be handy when you're going to be hauling a heavy load or a big trailer... but that's based on the idea that E85 does the same thing in a truck that it does in the 1.4T Sonic.

 

[Z71]

I tried two tankfuls of Shell 93 octane E10. Whereas fuel economy has not improved, the engine felt stronger when accelerating. I contribute this to ignition timing being able to advance more without pinging, which is detected by the knock sensor, which then retards timing.

 

[Swordsmith]

I tried two tankfuls of Shell 93 octane E10. Whereas fuel economy has not improved, the engine felt stronger when accelerating. I contribute this to ignition timing being able to advance more without pinging, which is detected by the knock sensor, which then retards timing.

Yes, that's the mechanism in a nutshell. It's a 106 octane engine which will retard timing to run whatever lower octane you end up putting in it, at the cost of some performance. Since most engines are 87 octane engines, the common advice that putting anything higher octane in is a waste, is generally correct. It just doesn't happen to apply here.

 

[sarrm]

I had 87 in my car when I got it from the dealer and my L per 100km was sitting at a ****ty 11 L per 100km. I now use only premium gas and my car doesnt budge off a 10.2 L per 100km so I definatly see the diffence using the more exspensive gas and would recommend it to everyone. Hoping to get even better gas mileage as it starts to warm up. 2012 chevy sonic ls. 48,200km on her going strong